diff --git a/src/config.cpp b/src/config.cpp
index aa2b592a8..caa4be15b 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -2253,7 +2253,6 @@ standardConfig configs[] = {
     createIntConfig("list-compress-depth", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, g_pserver->list_compress_depth, 0, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("rdb-key-save-delay", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, g_pserver->rdb_key_save_delay, 0, INTEGER_CONFIG, NULL, NULL),
     createIntConfig("key-load-delay", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, g_pserver->key_load_delay, 0, INTEGER_CONFIG, NULL, NULL),
-    createIntConfig("tracking-table-max-fill", NULL, MODIFIABLE_CONFIG, 0, 100, g_pserver->tracking_table_max_fill, 10, INTEGER_CONFIG, NULL, NULL), /* Default: 10% tracking table max fill. */
     createIntConfig("active-expire-effort", NULL, MODIFIABLE_CONFIG, 1, 10, cserver.active_expire_effort, 1, INTEGER_CONFIG, NULL, NULL), /* From 1 to 10. */
     createIntConfig("hz", NULL, MODIFIABLE_CONFIG, 0, INT_MAX, g_pserver->config_hz, CONFIG_DEFAULT_HZ, INTEGER_CONFIG, NULL, updateHZ),
     createIntConfig("min-replicas-to-write", "min-slaves-to-write", MODIFIABLE_CONFIG, 0, INT_MAX, g_pserver->repl_min_slaves_to_write, 0, INTEGER_CONFIG, NULL, updateGoodSlaves),
@@ -2288,6 +2287,7 @@ standardConfig configs[] = {
     createSizeTConfig("stream-node-max-bytes", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, g_pserver->stream_node_max_bytes, 4096, MEMORY_CONFIG, NULL, NULL),
     createSizeTConfig("zset-max-ziplist-value", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, g_pserver->zset_max_ziplist_value, 64, MEMORY_CONFIG, NULL, NULL),
     createSizeTConfig("hll-sparse-max-bytes", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, g_pserver->hll_sparse_max_bytes, 3000, MEMORY_CONFIG, NULL, NULL),
+    createSizeTConfig("tracking-table-max-keys", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, g_pserver->tracking_table_max_keys, 1000000, INTEGER_CONFIG, NULL, NULL), /* Default: 1 million keys max. */
 
     /* Other configs */
     createTimeTConfig("repl-backlog-ttl", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, g_pserver->repl_backlog_time_limit, 60*60, INTEGER_CONFIG, NULL, NULL), /* Default: 1 hour */
diff --git a/src/db.cpp b/src/db.cpp
index e71bf89c6..4b48f8df3 100644
--- a/src/db.cpp
+++ b/src/db.cpp
@@ -1550,8 +1550,10 @@ int expireIfNeeded(redisDb *db, robj *key) {
     propagateExpire(db,key,g_pserver->lazyfree_lazy_expire);
     notifyKeyspaceEvent(NOTIFY_EXPIRED,
         "expired",key,db->id);
-    return g_pserver->lazyfree_lazy_expire ? dbAsyncDelete(db,key) :
-                                         dbSyncDelete(db,key);
+    int retval = g_pserver->lazyfree_lazy_expire ? dbAsyncDelete(db,key) :
+                                               dbSyncDelete(db,key);
+    if (retval) signalModifiedKey(db,key);
+    return retval;
 }
 
 /* -----------------------------------------------------------------------------
diff --git a/src/defrag.cpp b/src/defrag.cpp
index 97297b8e5..767da9def 100644
--- a/src/defrag.cpp
+++ b/src/defrag.cpp
@@ -5,8 +5,8 @@
  * We do that by scanning the keyspace and for each pointer we have, we can try to
  * ask the allocator if moving it to a new address will help reduce fragmentation.
  *
- * Copyright (c) 2017, Oran Agra
- * Copyright (c) 2017, Redis Labs, Inc
+ * Copyright (c) 2020, Oran Agra
+ * Copyright (c) 2020, Redis Labs, Inc
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -421,25 +421,32 @@ bool replaceSateliteOSetKeyPtr(expireset &set, sds oldkey, sds newkey) {
     return false;
 }
 
-long activeDefragQuickListNodes(quicklist *ql) {
-    quicklistNode *node = ql->head, *newnode;
+long activeDefragQuickListNode(quicklist *ql, quicklistNode **node_ref) {
+    quicklistNode *newnode, *node = *node_ref;
     long defragged = 0;
     unsigned char *newzl;
+    if ((newnode = (quicklistNode*)activeDefragAlloc(node))) {
+        if (newnode->prev)
+            newnode->prev->next = newnode;
+        else
+            ql->head = newnode;
+        if (newnode->next)
+            newnode->next->prev = newnode;
+        else
+            ql->tail = newnode;
+        *node_ref = node = newnode;
+        defragged++;
+    }
+    if ((newzl = (unsigned char*)activeDefragAlloc(node->zl)))
+        defragged++, node->zl = newzl;
+    return defragged;
+}
+
+long activeDefragQuickListNodes(quicklist *ql) {
+    quicklistNode *node = ql->head;
+    long defragged = 0;
     while (node) {
-        if ((newnode = (quicklistNode*)activeDefragAlloc(node))) {
-            if (newnode->prev)
-                newnode->prev->next = newnode;
-            else
-                ql->head = newnode;
-            if (newnode->next)
-                newnode->next->prev = newnode;
-            else
-                ql->tail = newnode;
-            node = newnode;
-            defragged++;
-        }
-        if ((newzl = (unsigned char*)activeDefragAlloc(node->zl)))
-            defragged++, node->zl = newzl;
+        defragged += activeDefragQuickListNode(ql, &node);
         node = node->next;
     }
     return defragged;
@@ -453,12 +460,48 @@ void defragLater(redisDb *db, dictEntry *kde) {
     listAddNodeTail(db->defrag_later, key);
 }
 
-long scanLaterList(robj *ob) {
+/* returns 0 if no more work needs to be been done, and 1 if time is up and more work is needed. */
+long scanLaterList(robj *ob, unsigned long *cursor, long long endtime, long long *defragged) {
     quicklist *ql = (quicklist*)ptrFromObj(ob);
+    quicklistNode *node;
+    long iterations = 0;
+    int bookmark_failed = 0;
     if (ob->type != OBJ_LIST || ob->encoding != OBJ_ENCODING_QUICKLIST)
         return 0;
-    g_pserver->stat_active_defrag_scanned+=ql->len;
-    return activeDefragQuickListNodes(ql);
+
+    if (*cursor == 0) {
+        /* if cursor is 0, we start new iteration */
+        node = ql->head;
+    } else {
+        node = quicklistBookmarkFind(ql, "_AD");
+        if (!node) {
+            /* if the bookmark was deleted, it means we reached the end. */
+            *cursor = 0;
+            return 0;
+        }
+        node = node->next;
+    }
+
+    (*cursor)++;
+    while (node) {
+        (*defragged) += activeDefragQuickListNode(ql, &node);
+        g_pserver->stat_active_defrag_scanned++;
+        if (++iterations > 128 && !bookmark_failed) {
+            if (ustime() > endtime) {
+                if (!quicklistBookmarkCreate(&ql, "_AD", node)) {
+                    bookmark_failed = 1;
+                } else {
+                    ob->m_ptr = ql; /* bookmark creation may have re-allocated the quicklist */
+                    return 1;
+                }
+            }
+            iterations = 0;
+        }
+        node = node->next;
+    }
+    quicklistBookmarkDelete(ql, "_AD");
+    *cursor = 0;
+    return bookmark_failed? 1: 0;
 }
 
 typedef struct {
@@ -651,7 +694,8 @@ int scanLaterStraemListpacks(robj *ob, unsigned long *cursor, long long endtime,
         void *newdata = activeDefragAlloc(ri.data);
         if (newdata)
             raxSetData(ri.node, ri.data=newdata), (*defragged)++;
-        if (++iterations > 16) {
+        g_pserver->stat_active_defrag_scanned++;
+        if (++iterations > 128) {
             if (ustime() > endtime) {
                 serverAssert(ri.key_len==sizeof(last));
                 memcpy(last,ri.key,ri.key_len);
@@ -916,8 +960,7 @@ int defragLaterItem(dictEntry *de, unsigned long *cursor, long long endtime) {
     if (de) {
         robj *ob = (robj*)dictGetVal(de);
         if (ob->type == OBJ_LIST) {
-            g_pserver->stat_active_defrag_hits += scanLaterList(ob);
-            *cursor = 0; /* list has no scan, we must finish it in one go */
+            return scanLaterList(ob, cursor, endtime, &g_pserver->stat_active_defrag_hits);
         } else if (ob->type == OBJ_SET) {
             g_pserver->stat_active_defrag_hits += scanLaterSet(ob, cursor);
         } else if (ob->type == OBJ_ZSET) {
@@ -977,11 +1020,6 @@ int defragLaterStep(redisDb *db, long long endtime) {
             if (defragLaterItem(de, &defrag_later_cursor, endtime))
                 quit = 1; /* time is up, we didn't finish all the work */
 
-            /* Don't start a new BIG key in this loop, this is because the
-             * next key can be a list, and scanLaterList must be done in once cycle */
-            if (!defrag_later_cursor)
-                quit = 1;
-
             /* Once in 16 scan iterations, 512 pointer reallocations, or 64 fields
              * (if we have a lot of pointers in one hash bucket, or rehashing),
              * check if we reached the time limit. */
diff --git a/src/networking.cpp b/src/networking.cpp
index 4d60ac1ff..1c8d561e6 100644
--- a/src/networking.cpp
+++ b/src/networking.cpp
@@ -176,6 +176,7 @@ client *createClient(connection *conn, int iel) {
     c->master_error = 0;
     memset(c->uuid, 0, UUID_BINARY_LEN);
 
+    c->client_tracking_prefixes = NULL;
     c->auth_callback = NULL;
     c->auth_callback_privdata = NULL;
     c->auth_module = NULL;
@@ -2584,7 +2585,6 @@ int clientSetNameOrReply(client *c, robj *name) {
 void clientCommand(client *c) {
     listNode *ln;
     listIter li;
-    client *client;
 
     if (c->argc == 2 && !strcasecmp((const char*)ptrFromObj(c->argv[1]),"help")) {
         const char *help[] = {
@@ -2698,7 +2698,7 @@ NULL
         /* Iterate clients killing all the matching clients. */
         listRewind(g_pserver->clients,&li);
         while ((ln = listNext(&li)) != NULL) {
-            client = (struct client*)listNodeValue(ln);
+            client *client = (struct client*)listNodeValue(ln);
             if (addr && strcmp(getClientPeerId(client),addr) != 0) continue;
             if (type != -1 && getClientType(client) != type) continue;
             if (id != 0 && client->id != id) continue;
@@ -2787,38 +2787,74 @@ NULL
                 UNIT_MILLISECONDS) != C_OK) return;
         pauseClients(duration);
         addReply(c,shared.ok);
-    } else if (!strcasecmp(szFromObj(c->argv[1]),"tracking") &&
-               (c->argc == 3 || c->argc == 5))
-    {
-        /* CLIENT TRACKING (on|off) [REDIRECT <id>] */
+    } else if (!strcasecmp(szFromObj(c->argv[1]),"tracking") && c->argc >= 3) {
+        /* CLIENT TRACKING (on|off) [REDIRECT <id>] [BCAST] [PREFIX first]
+         *                          [PREFIX second] ... */
         long long redir = 0;
+        int bcast = 0;
+        robj **prefix = NULL;
+        size_t numprefix = 0;
 
-        /* Parse the redirection option: we'll require the client with
-         * the specified ID to exist right now, even if it is possible
-         * it will get disconnected later. */
-        if (c->argc == 5) {
-            if (strcasecmp(szFromObj(c->argv[3]),"redirect") != 0) {
-                addReply(c,shared.syntaxerr);
-                return;
-            } else {
-                if (getLongLongFromObjectOrReply(c,c->argv[4],&redir,NULL) !=
+        /* Parse the options. */
+        for (int j = 3; j < c->argc; j++) {
+            int moreargs = (c->argc-1) - j;
+
+            if (!strcasecmp(szFromObj(c->argv[j]),"redirect") && moreargs) {
+                j++;
+                if (getLongLongFromObjectOrReply(c,c->argv[j],&redir,NULL) !=
                     C_OK) return;
+                /* We will require the client with the specified ID to exist
+                 * right now, even if it is possible that it gets disconnected
+                 * later. Still a valid sanity check. */
                 if (lookupClientByID(redir) == NULL) {
                     addReplyError(c,"The client ID you want redirect to "
                                     "does not exist");
                     return;
                 }
+            } else if (!strcasecmp(szFromObj(c->argv[j]),"bcast")) {
+                bcast++;
+            } else if (!strcasecmp(szFromObj(c->argv[j]),"prefix") && moreargs) {
+                j++;
+                prefix = (robj**)zrealloc(prefix,sizeof(robj*)*(numprefix+1), MALLOC_LOCAL);
+                prefix[numprefix++] = c->argv[j];
+            } else {
+                zfree(prefix);
+                addReply(c,shared.syntaxerr);
+                return;
             }
         }
 
+        /* Options are ok: enable or disable the tracking for this client. */
         if (!strcasecmp(szFromObj(c->argv[2]),"on")) {
-            enableTracking(c,redir);
+            /* Before enabling tracking, make sure options are compatible
+             * among each other and with the current state of the client. */
+            if (!bcast && numprefix) {
+                addReplyError(c,
+                    "PREFIX option requires BCAST mode to be enabled");
+                zfree(prefix);
+                return;
+            }
+
+            if (c->flags & CLIENT_TRACKING) {
+                int oldbcast = !!(c->flags & CLIENT_TRACKING_BCAST);
+                if (oldbcast != bcast) {
+                    addReplyError(c,
+                    "You can't switch BCAST mode on/off before disabling "
+                    "tracking for this client, and then re-enabling it with "
+                    "a different mode.");
+                    zfree(prefix);
+                    return;
+                }
+            }
+            enableTracking(c,redir,bcast,prefix,numprefix);
         } else if (!strcasecmp(szFromObj(c->argv[2]),"off")) {
             disableTracking(c);
         } else {
+            zfree(prefix);
             addReply(c,shared.syntaxerr);
             return;
         }
+        zfree(prefix);
         addReply(c,shared.ok);
     } else if (!strcasecmp(szFromObj(c->argv[1]),"getredir") && c->argc == 2) {
         /* CLIENT GETREDIR */
diff --git a/src/object.cpp b/src/object.cpp
index 2692e6308..8ef69a0eb 100644
--- a/src/object.cpp
+++ b/src/object.cpp
@@ -1151,13 +1151,13 @@ sds getMemoryDoctorReport(void) {
             num_reports++;
         }
 
-        /* Allocator fss is higher than 1.1 and 10MB ? */
+        /* Allocator rss is higher than 1.1 and 10MB ? */
         if (mh->allocator_rss > 1.1 && mh->allocator_rss_bytes > 10<<20) {
             high_alloc_rss = 1;
             num_reports++;
         }
 
-        /* Non-Allocator fss is higher than 1.1 and 10MB ? */
+        /* Non-Allocator rss is higher than 1.1 and 10MB ? */
         if (mh->rss_extra > 1.1 && mh->rss_extra_bytes > 10<<20) {
             high_proc_rss = 1;
             num_reports++;
diff --git a/src/pubsub.cpp b/src/pubsub.cpp
index 0c657a588..661124c1c 100644
--- a/src/pubsub.cpp
+++ b/src/pubsub.cpp
@@ -35,7 +35,11 @@ int clientSubscriptionsCount(client *c);
  * Pubsub client replies API
  *----------------------------------------------------------------------------*/
 
-/* Send a pubsub message of type "message" to the client. */
+/* Send a pubsub message of type "message" to the client.
+ * Normally 'msg' is a Redis object containing the string to send as
+ * message. However if the caller sets 'msg' as NULL, it will be able
+ * to send a special message (for instance an Array type) by using the
+ * addReply*() API family. */
 void addReplyPubsubMessage(client *c, robj *channel, robj *msg) {
     if (c->resp == 2)
         addReplyAsync(c,shared.mbulkhdr[3]);
@@ -43,7 +47,7 @@ void addReplyPubsubMessage(client *c, robj *channel, robj *msg) {
         addReplyPushLenAsync(c,3);
     addReplyAsync(c,shared.messagebulk);
     addReplyBulkAsync(c,channel);
-    addReplyBulkAsync(c,msg);
+    if (msg) addReplyBulkAsync(c,msg);
 }
 
 /* Send a pubsub message of type "pmessage" to the client. The difference
diff --git a/src/quicklist.c b/src/quicklist.c
index 2f5eab215..0385e0bf9 100644
--- a/src/quicklist.c
+++ b/src/quicklist.c
@@ -70,6 +70,12 @@ static const size_t optimization_level[] = {4096, 8192, 16384, 32768, 65536};
     } while (0);
 #endif
 
+/* Bookmarks forward declarations */
+#define QL_MAX_BM ((1 << QL_BM_BITS)-1)
+quicklistBookmark *_quicklistBookmarkFindByName(quicklist *ql, const char *name);
+quicklistBookmark *_quicklistBookmarkFindByNode(quicklist *ql, quicklistNode *node);
+void _quicklistBookmarkDelete(quicklist *ql, quicklistBookmark *bm);
+
 /* Simple way to give quicklistEntry structs default values with one call. */
 #define initEntry(e)                                                           \
     do {                                                                       \
@@ -100,10 +106,11 @@ quicklist *quicklistCreate(void) {
     quicklist->count = 0;
     quicklist->compress = 0;
     quicklist->fill = -2;
+    quicklist->bookmark_count = 0;
     return quicklist;
 }
 
-#define COMPRESS_MAX (1 << 16)
+#define COMPRESS_MAX (1 << QL_COMP_BITS)
 void quicklistSetCompressDepth(quicklist *quicklist, int compress) {
     if (compress > COMPRESS_MAX) {
         compress = COMPRESS_MAX;
@@ -113,7 +120,7 @@ void quicklistSetCompressDepth(quicklist *quicklist, int compress) {
     quicklist->compress = compress;
 }
 
-#define FILL_MAX (1 << 15)
+#define FILL_MAX (1 << (QL_FILL_BITS-1))
 void quicklistSetFill(quicklist *quicklist, int fill) {
     if (fill > FILL_MAX) {
         fill = FILL_MAX;
@@ -169,6 +176,7 @@ void quicklistRelease(quicklist *quicklist) {
         quicklist->len--;
         current = next;
     }
+    quicklistBookmarksClear(quicklist);
     zfree(quicklist);
 }
 
@@ -578,6 +586,15 @@ quicklist *quicklistCreateFromZiplist(int fill, int compress,
 
 REDIS_STATIC void __quicklistDelNode(quicklist *quicklist,
                                      quicklistNode *node) {
+    /* Update the bookmark if any */
+    quicklistBookmark *bm = _quicklistBookmarkFindByNode(quicklist, node);
+    if (bm) {
+        bm->node = node->next;
+        /* if the bookmark was to the last node, delete it. */
+        if (!bm->node)
+            _quicklistBookmarkDelete(quicklist, bm);
+    }
+
     if (node->next)
         node->next->prev = node->prev;
     if (node->prev)
@@ -1410,6 +1427,87 @@ void quicklistPush(quicklist *quicklist, void *value, const size_t sz,
     }
 }
 
+/* Create or update a bookmark in the list which will be updated to the next node
+ * automatically when the one referenced gets deleted.
+ * Returns 1 on success (creation of new bookmark or override of an existing one).
+ * Returns 0 on failure (reached the maximum supported number of bookmarks).
+ * NOTE: use short simple names, so that string compare on find is quick.
+ * NOTE: bookmakrk creation may re-allocate the quicklist, so the input pointer
+         may change and it's the caller responsibilty to update the reference.
+ */
+int quicklistBookmarkCreate(quicklist **ql_ref, const char *name, quicklistNode *node) {
+    quicklist *ql = *ql_ref;
+    if (ql->bookmark_count >= QL_MAX_BM)
+        return 0;
+    quicklistBookmark *bm = _quicklistBookmarkFindByName(ql, name);
+    if (bm) {
+        bm->node = node;
+        return 1;
+    }
+    ql = zrealloc(ql, sizeof(quicklist) + (ql->bookmark_count+1) * sizeof(quicklistBookmark), MALLOC_SHARED);
+    *ql_ref = ql;
+    ql->bookmarks[ql->bookmark_count].node = node;
+    ql->bookmarks[ql->bookmark_count].name = zstrdup(name);
+    ql->bookmark_count++;
+    return 1;
+}
+
+/* Find the quicklist node referenced by a named bookmark.
+ * When the bookmarked node is deleted the bookmark is updated to the next node,
+ * and if that's the last node, the bookmark is deleted (so find returns NULL). */
+quicklistNode *quicklistBookmarkFind(quicklist *ql, const char *name) {
+    quicklistBookmark *bm = _quicklistBookmarkFindByName(ql, name);
+    if (!bm) return NULL;
+    return bm->node;
+}
+
+/* Delete a named bookmark.
+ * returns 0 if bookmark was not found, and 1 if deleted.
+ * Note that the bookmark memory is not freed yet, and is kept for future use. */
+int quicklistBookmarkDelete(quicklist *ql, const char *name) {
+    quicklistBookmark *bm = _quicklistBookmarkFindByName(ql, name);
+    if (!bm)
+        return 0;
+    _quicklistBookmarkDelete(ql, bm);
+    return 1;
+}
+
+quicklistBookmark *_quicklistBookmarkFindByName(quicklist *ql, const char *name) {
+    unsigned i;
+    for (i=0; i<ql->bookmark_count; i++) {
+        if (!strcmp(ql->bookmarks[i].name, name)) {
+            return &ql->bookmarks[i];
+        }
+    }
+    return NULL;
+}
+
+quicklistBookmark *_quicklistBookmarkFindByNode(quicklist *ql, quicklistNode *node) {
+    unsigned i;
+    for (i=0; i<ql->bookmark_count; i++) {
+        if (ql->bookmarks[i].node == node) {
+            return &ql->bookmarks[i];
+        }
+    }
+    return NULL;
+}
+
+void _quicklistBookmarkDelete(quicklist *ql, quicklistBookmark *bm) {
+    int index = bm - ql->bookmarks;
+    zfree(bm->name);
+    ql->bookmark_count--;
+    memmove(bm, bm+1, (ql->bookmark_count - index)* sizeof(*bm));
+    /* NOTE: We do not shrink (realloc) the quicklist yet (to avoid resonance,
+     * it may be re-used later (a call to realloc may NOP). */
+}
+
+void quicklistBookmarksClear(quicklist *ql) {
+    while (ql->bookmark_count)
+        zfree(ql->bookmarks[--ql->bookmark_count].name);
+    /* NOTE: We do not shrink (realloc) the quick list. main use case for this
+     * function is just before releasing the allocation. */
+}
+
 /* The rest of this file is test cases and test helpers. */
 #ifdef REDIS_TEST
 #include <stdint.h>
@@ -2641,6 +2739,54 @@ int quicklistTest(int argc, char *argv[]) {
     printf("Compressions: %0.2f seconds.\n", (float)(stop - start) / 1000);
     printf("\n");
 
+    TEST("bookmark get updated to next item") {
+        quicklist *ql = quicklistNew(1, 0);
+        quicklistPushTail(ql, "1", 1);
+        quicklistPushTail(ql, "2", 1);
+        quicklistPushTail(ql, "3", 1);
+        quicklistPushTail(ql, "4", 1);
+        quicklistPushTail(ql, "5", 1);
+        assert(ql->len==5);
+        /* add two bookmarks, one pointing to the node before the last. */
+        assert(quicklistBookmarkCreate(&ql, "_dummy", ql->head->next));
+        assert(quicklistBookmarkCreate(&ql, "_test", ql->tail->prev));
+        /* test that the bookmark returns the right node, delete it and see that the bookmark points to the last node */
+        assert(quicklistBookmarkFind(ql, "_test") == ql->tail->prev);
+        assert(quicklistDelRange(ql, -2, 1));
+        assert(quicklistBookmarkFind(ql, "_test") == ql->tail);
+        /* delete the last node, and see that the bookmark was deleted. */
+        assert(quicklistDelRange(ql, -1, 1));
+        assert(quicklistBookmarkFind(ql, "_test") == NULL);
+        /* test that other bookmarks aren't affected */
+        assert(quicklistBookmarkFind(ql, "_dummy") == ql->head->next);
+        assert(quicklistBookmarkFind(ql, "_missing") == NULL);
+        assert(ql->len==3);
+        quicklistBookmarksClear(ql); /* for coverage */
+        assert(quicklistBookmarkFind(ql, "_dummy") == NULL);
+        quicklistRelease(ql);
+    }
+
+    TEST("bookmark limit") {
+        int i;
+        quicklist *ql = quicklistNew(1, 0);
+        quicklistPushHead(ql, "1", 1);
+        for (i=0; i<QL_MAX_BM; i++)
+            assert(quicklistBookmarkCreate(&ql, genstr("",i), ql->head));
+        /* when all bookmarks are used, creation fails */
+        assert(!quicklistBookmarkCreate(&ql, "_test", ql->head));
+        /* delete one and see that we can now create another */
+        assert(quicklistBookmarkDelete(ql, "0"));
+        assert(quicklistBookmarkCreate(&ql, "_test", ql->head));
+        /* delete one and see that the rest survive */
+        assert(quicklistBookmarkDelete(ql, "_test"));
+        for (i=1; i<QL_MAX_BM; i++)
+            assert(quicklistBookmarkFind(ql, genstr("",i)) == ql->head);
+        /* make sure the deleted ones are indeed gone */
+        assert(!quicklistBookmarkFind(ql, "0"));
+        assert(!quicklistBookmarkFind(ql, "_test"));
+        quicklistRelease(ql);
+    }
+
     if (!err)
         printf("ALL TESTS PASSED!\n");
     else
diff --git a/src/quicklist.h b/src/quicklist.h
index 18619ad86..70b67d942 100644
--- a/src/quicklist.h
+++ b/src/quicklist.h
@@ -28,6 +28,8 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <stdint.h> // for UINTPTR_MAX
+
 #ifndef __QUICKLIST_H__
 #define __QUICKLIST_H__
 
@@ -72,19 +74,53 @@ typedef struct quicklistLZF {
 #endif
 } quicklistLZF;
 
+/* Bookmarks are padded with realloc at the end of of the quicklist struct.
+ * They should only be used for very big lists if thousands of nodes were the
+ * excess memory usage is negligible, and there's a real need to iterate on them
+ * in portions.
+ * When not used, they don't add any memory overhead, but when used and then
+ * deleted, some overhead remains (to avoid resonance).
+ * The number of bookmarks used should be kept to minimum since it also adds
+ * overhead on node deletion (searching for a bookmark to update). */
+typedef struct quicklistBookmark {
+    quicklistNode *node;
+    char *name;
+} quicklistBookmark;
+
+#if UINTPTR_MAX == 0xffffffff
+/* 32-bit */
+#   define QL_FILL_BITS 14
+#   define QL_COMP_BITS 14
+#   define QL_BM_BITS 4
+#elif UINTPTR_MAX == 0xffffffffffffffff
+/* 64-bit */
+#   define QL_FILL_BITS 16
+#   define QL_COMP_BITS 16
+#   define QL_BM_BITS 4 /* we can encode more, but we rather limit the user
+                           since they cause performance degradation. */
+#else
+#   error unknown arch bits count
+#endif
+
 /* quicklist is a 40 byte struct (on 64-bit systems) describing a quicklist.
  * 'count' is the number of total entries.
  * 'len' is the number of quicklist nodes.
  * 'compress' is: -1 if compression disabled, otherwise it's the number
  *                of quicklistNodes to leave uncompressed at ends of quicklist.
- * 'fill' is the user-requested (or default) fill factor. */
+ * 'fill' is the user-requested (or default) fill factor.
+ * 'bookmakrs are an optional feature that is used by realloc this struct,
+ *      so that they don't consume memory when not used. */
 typedef struct quicklist {
     quicklistNode *head;
     quicklistNode *tail;
     unsigned long count;        /* total count of all entries in all ziplists */
     unsigned long len;          /* number of quicklistNodes */
-    int fill : 16;              /* fill factor for individual nodes */
-    unsigned int compress : 16; /* depth of end nodes not to compress;0=off */
+    int fill : QL_FILL_BITS;              /* fill factor for individual nodes */
+    unsigned int compress : QL_COMP_BITS; /* depth of end nodes not to compress;0=off */
+    unsigned int bookmark_count: QL_BM_BITS;
+#ifndef __cplusplus
+    quicklistBookmark bookmarks[];
+#endif
 } quicklist;
 
 typedef struct quicklistIter {
@@ -170,6 +206,12 @@ unsigned long quicklistCount(const quicklist *ql);
 int quicklistCompare(unsigned char *p1, unsigned char *p2, int p2_len);
 size_t quicklistGetLzf(const quicklistNode *node, void **data);
 
+/* bookmarks */
+int quicklistBookmarkCreate(quicklist **ql_ref, const char *name, quicklistNode *node);
+int quicklistBookmarkDelete(quicklist *ql, const char *name);
+quicklistNode *quicklistBookmarkFind(quicklist *ql, const char *name);
+void quicklistBookmarksClear(quicklist *ql);
+
 #ifdef REDIS_TEST
 int quicklistTest(int argc, char *argv[]);
 #endif
diff --git a/src/server.cpp b/src/server.cpp
index d7a378f98..d4426bbe4 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -2209,6 +2209,10 @@ void beforeSleep(struct aeEventLoop *eventLoop) {
         processUnblockedClients(IDX_EVENT_LOOP_MAIN);
     }
 
+    /* Send the invalidation messages to clients participating to the
+     * client side caching protocol in broadcasting (BCAST) mode. */
+    trackingBroadcastInvalidationMessages();
+
     /* Write the AOF buffer on disk */
     flushAppendOnlyFile(0);
 
@@ -3526,8 +3530,11 @@ void call(client *c, int flags) {
     if (c->cmd->flags & CMD_READONLY) {
         client *caller = (c->flags & CLIENT_LUA && g_pserver->lua_caller) ?
                             g_pserver->lua_caller : c;
-        if (caller->flags & CLIENT_TRACKING)
+        if (caller->flags & CLIENT_TRACKING &&
+            !(caller->flags & CLIENT_TRACKING_BCAST))
+        {
             trackingRememberKeys(caller);
+        }
     }
 
     g_pserver->stat_numcommands++;
@@ -4477,6 +4484,7 @@ sds genRedisInfoString(const char *section) {
             "active_defrag_misses:%lld\r\n"
             "active_defrag_key_hits:%lld\r\n"
             "active_defrag_key_misses:%lld\r\n"
+            "tracking_total_keys:%lld\r\n"
             "tracking_total_items:%llu\r\n",
             g_pserver->stat_numconnections,
             g_pserver->stat_numcommands,
@@ -4505,6 +4513,7 @@ sds genRedisInfoString(const char *section) {
             g_pserver->stat_active_defrag_misses,
             g_pserver->stat_active_defrag_key_hits,
             g_pserver->stat_active_defrag_key_misses,
+            (unsigned long long) trackingGetTotalKeys(),
             (unsigned long long) trackingGetTotalItems());
     }
 
diff --git a/src/server.h b/src/server.h
index c55eb9ee6..bb3f65c25 100644
--- a/src/server.h
+++ b/src/server.h
@@ -412,6 +412,7 @@ public:
                                    perform client side caching. */
 #define CLIENT_TRACKING_BROKEN_REDIR (1ULL<<32) /* Target client is invalid. */
 #define CLIENT_FORCE_REPLY (1ULL<<33) /* Should addReply be forced to write the text? */
+#define CLIENT_TRACKING_BCAST (1ULL<<34) /* Tracking in BCAST mode. */
 
 /* Client block type (btype field in client structure)
  * if CLIENT_BLOCKED flag is set. */
@@ -1298,7 +1299,9 @@ typedef struct client {
      * invalidation messages for keys fetched by this client will be send to
      * the specified client ID. */
     uint64_t client_tracking_redirection;
-
+    rax *client_tracking_prefixes; /* A dictionary of prefixes we are already
+                                      subscribed to in BCAST mode, in the
+                                      context of client side caching. */
     /* Response buffer */
     int bufpos;
     char buf[PROTO_REPLY_CHUNK_BYTES];
@@ -1848,7 +1851,7 @@ struct redisServer {
     list *ready_keys;        /* List of readyList structures for BLPOP & co */
     /* Client side caching. */
     unsigned int tracking_clients;  /* # of clients with tracking enabled.*/
-    int tracking_table_max_fill;    /* Max fill percentage. */
+    size_t tracking_table_max_keys; /* Max number of keys in tracking table. */
     /* Sort parameters - qsort_r() is only available under BSD so we
      * have to take this state global, in order to pass it to sortCompare() */
     int sort_desc;
@@ -2224,13 +2227,15 @@ void addReplyStatusFormat(client *c, const char *fmt, ...);
 #endif
 
 /* Client side caching (tracking mode) */
-void enableTracking(client *c, uint64_t redirect_to);
+void enableTracking(client *c, uint64_t redirect_to, int bcast, robj **prefix, size_t numprefix);
 void disableTracking(client *c);
 void trackingRememberKeys(client *c);
 void trackingInvalidateKey(robj *keyobj);
 void trackingInvalidateKeysOnFlush(int dbid);
 void trackingLimitUsedSlots(void);
 uint64_t trackingGetTotalItems(void);
+uint64_t trackingGetTotalKeys(void);
+void trackingBroadcastInvalidationMessages(void);
 
 /* List data type */
 void listTypeTryConversion(robj *subject, robj *value);
diff --git a/src/t_stream.cpp b/src/t_stream.cpp
index 11d0e3b07..cd69dbe93 100644
--- a/src/t_stream.cpp
+++ b/src/t_stream.cpp
@@ -1856,6 +1856,8 @@ NULL
             g_pserver->dirty++;
             notifyKeyspaceEvent(NOTIFY_STREAM,"xgroup-destroy",
                                 c->argv[2],c->db->id);
+            /* We want to unblock any XREADGROUP consumers with -NOGROUP. */
+            signalKeyAsReady(c->db,c->argv[2]);
         } else {
             addReply(c,shared.czero);
         }
diff --git a/src/tracking.cpp b/src/tracking.cpp
index baf5ddbc8..50f03c946 100644
--- a/src/tracking.cpp
+++ b/src/tracking.cpp
@@ -42,12 +42,22 @@
  * Clients will normally take frequently requested objects in memory, removing
  * them when invalidation messages are received. */
 rax *TrackingTable = NULL;
+rax *PrefixTable = NULL;
 uint64_t TrackingTableTotalItems = 0; /* Total number of IDs stored across
                                          the whole tracking table. This givesn
                                          an hint about the total memory we
                                          are using server side for CSC. */
 robj *TrackingChannelName;
 
+/* This is the structure that we have as value of the PrefixTable, and
+ * represents the list of keys modified, and the list of clients that need
+ * to be notified, for a given prefix. */
+typedef struct bcastState {
+    rax *keys;      /* Keys modified in the current event loop cycle. */
+    rax *clients;   /* Clients subscribed to the notification events for this
+                       prefix. */
+} bcastState;
+
 /* Remove the tracking state from the client 'c'. Note that there is not much
  * to do for us here, if not to decrement the counter of the clients in
  * tracking mode, because we just store the ID of the client in the tracking
@@ -55,9 +65,55 @@ robj *TrackingChannelName;
  * client with many entries in the table is removed, it would cost a lot of
  * time to do the cleanup. */
 void disableTracking(client *c) {
+    /* If this client is in broadcasting mode, we need to unsubscribe it
+     * from all the prefixes it is registered to. */
+    if (c->flags & CLIENT_TRACKING_BCAST) {
+        raxIterator ri;
+        raxStart(&ri,c->client_tracking_prefixes);
+        raxSeek(&ri,"^",NULL,0);
+        while(raxNext(&ri)) {
+            bcastState *bs = (bcastState*)raxFind(PrefixTable,ri.key,ri.key_len);
+            serverAssert(bs != raxNotFound);
+            raxRemove(bs->clients,(unsigned char*)&c,sizeof(c),NULL);
+            /* Was it the last client? Remove the prefix from the
+             * table. */
+            if (raxSize(bs->clients) == 0) {
+                raxFree(bs->clients);
+                raxFree(bs->keys);
+                zfree(bs);
+                raxRemove(PrefixTable,ri.key,ri.key_len,NULL);
+            }
+        }
+        raxStop(&ri);
+        raxFree(c->client_tracking_prefixes);
+        c->client_tracking_prefixes = NULL;
+    }
+
+    /* Clear flags and adjust the count. */
     if (c->flags & CLIENT_TRACKING) {
         g_pserver->tracking_clients--;
-        c->flags &= ~(CLIENT_TRACKING|CLIENT_TRACKING_BROKEN_REDIR);
+        c->flags &= ~(CLIENT_TRACKING|CLIENT_TRACKING_BROKEN_REDIR|
+                      CLIENT_TRACKING_BCAST);
+    }
+}
+
+/* Set the client 'c' to track the prefix 'prefix'. If the client 'c' is
+ * already registered for the specified prefix, no operation is performed. */
+void enableBcastTrackingForPrefix(client *c, const char *prefix, size_t plen) {
+    bcastState *bs = (bcastState*)raxFind(PrefixTable,(unsigned char*)prefix,sdslen(prefix));
+    /* If this is the first client subscribing to such prefix, create
+     * the prefix in the table. */
+    if (bs == raxNotFound) {
+        bs = (bcastState*)zmalloc(sizeof(*bs));
+        bs->keys = raxNew();
+        bs->clients = raxNew();
+        raxInsert(PrefixTable,(unsigned char*)prefix,plen,bs,NULL);
+    }
+    if (raxTryInsert(bs->clients,(unsigned char*)&c,sizeof(c),NULL,NULL)) {
+        if (c->client_tracking_prefixes == NULL)
+            c->client_tracking_prefixes = raxNew();
+        raxInsert(c->client_tracking_prefixes,
+                  (unsigned char*)prefix,plen,NULL,NULL);
     }
 }
 
@@ -68,16 +124,25 @@ void disableTracking(client *c) {
  * eventually get freed, we'll send a message to the original client to
  * inform it of the condition. Multiple clients can redirect the invalidation
  * messages to the same client ID. */
-void enableTracking(client *c, uint64_t redirect_to) {
-    if (c->flags & CLIENT_TRACKING) return;
+void enableTracking(client *c, uint64_t redirect_to, int bcast, robj **prefix, size_t numprefix) {
+    if (!(c->flags & CLIENT_TRACKING)) g_pserver->tracking_clients++;
     c->flags |= CLIENT_TRACKING;
-    c->flags &= ~CLIENT_TRACKING_BROKEN_REDIR;
+    c->flags &= ~(CLIENT_TRACKING_BROKEN_REDIR|CLIENT_TRACKING_BCAST);
     c->client_tracking_redirection = redirect_to;
-    g_pserver->tracking_clients++;
     if (TrackingTable == NULL) {
         TrackingTable = raxNew();
+        PrefixTable = raxNew();
         TrackingChannelName = createStringObject("__redis__:invalidate",20);
     }
+
+    if (bcast) {
+        c->flags |= CLIENT_TRACKING_BCAST;
+        if (numprefix == 0) enableBcastTrackingForPrefix(c,"",0);
+        for (size_t j = 0; j < numprefix; j++) {
+            sds sdsprefix = szFromObj(prefix[j]);
+            enableBcastTrackingForPrefix(c,sdsprefix,sdslen(sdsprefix));
+        }
+    }
 }
 
 /* This function is called after the excution of a readonly command in the
@@ -106,7 +171,17 @@ void trackingRememberKeys(client *c) {
     getKeysFreeResult(keys);
 }
 
-void sendTrackingMessage(client *c, const char *keyname, size_t keylen) {
+/* Given a key name, this function sends an invalidation message in the
+ * proper channel (depending on RESP version: PubSub or Push message) and
+ * to the proper client (in case fo redirection), in the context of the
+ * client 'c' with tracking enabled.
+ *
+ * In case the 'proto' argument is non zero, the function will assume that
+ * 'keyname' points to a buffer of 'keylen' bytes already expressed in the
+ * form of Redis RESP protocol, representing an array of keys to send
+ * to the client as value of the invalidation. This is used in BCAST mode
+ * in order to optimized the implementation to use less CPU time. */
+void sendTrackingMessage(client *c, const char *keyname, size_t keylen, int proto) {
     int using_redirection = 0;
     if (c->client_tracking_redirection) {
         client *redir = lookupClientByID(c->client_tracking_redirection);
@@ -132,15 +207,45 @@ void sendTrackingMessage(client *c, const char *keyname, size_t keylen) {
     if (c->resp > 2) {
         addReplyPushLen(c,2);
         addReplyBulkCBuffer(c,"invalidate",10);
-        addReplyBulkCBuffer(c,keyname,keylen);
     } else if (using_redirection && c->flags & CLIENT_PUBSUB) {
         /* We use a static object to speedup things, however we assume
          * that addReplyPubsubMessage() will not take a reference. */
-        robj keyobj;
-        initStaticStringObject(keyobj,(char*)keyname);
-        addReplyPubsubMessage(c,TrackingChannelName,&keyobj);
-        serverAssert(keyobj.getrefcount(std::memory_order_relaxed) == 1);
+        addReplyPubsubMessage(c,TrackingChannelName,NULL);
+    } else {
+        /* If are here, the client is not using RESP3, nor is
+         * redirecting to another client. We can't send anything to
+         * it since RESP2 does not support push messages in the same
+         * connection. */
+        return;
     }
+
+    /* Send the "value" part, which is the array of keys. */
+    if (proto) {
+        addReplyProto(c,keyname,keylen);
+    } else {
+        addReplyArrayLen(c,1);
+        addReplyBulkCBuffer(c,keyname,keylen);
+    }
+}
+
+/* This function is called when a key is modified in Redis and in the case
+ * we have at least one client with the BCAST mode enabled.
+ * Its goal is to set the key in the right broadcast state if the key
+ * matches one or more prefixes in the prefix table. Later when we
+ * return to the event loop, we'll send invalidation messages to the
+ * clients subscribed to each prefix. */
+void trackingRememberKeyToBroadcast(char *keyname, size_t keylen) {
+    raxIterator ri;
+    raxStart(&ri,PrefixTable);
+    raxSeek(&ri,"^",NULL,0);
+    while(raxNext(&ri)) {
+        if (ri.key_len > keylen) continue;
+        if (ri.key_len != 0 && memcmp(ri.key,keyname,ri.key_len) != 0)
+            continue;
+        bcastState *bs = (bcastState*)ri.data;
+        raxTryInsert(bs->keys,(unsigned char*)keyname,keylen,NULL,NULL);
+    }
+    raxStop(&ri);
 }
 
 /* This function is called from signalModifiedKey() or other places in Redis
@@ -150,6 +255,10 @@ void sendTrackingMessage(client *c, const char *keyname, size_t keylen) {
 void trackingInvalidateKey(robj *keyobj) {
     if (TrackingTable == NULL) return;
     sds sdskey = szFromObj(keyobj);
+
+    if (raxSize(PrefixTable) > 0)
+        trackingRememberKeyToBroadcast(sdskey,sdslen(sdskey));
+
     rax *ids = (rax*)raxFind(TrackingTable,(unsigned char*)sdskey,sdslen(sdskey));
     if (ids == raxNotFound) return;;
 
@@ -160,8 +269,18 @@ void trackingInvalidateKey(robj *keyobj) {
         uint64_t id;
         memcpy(&id,ri.key,sizeof(id));
         client *c = lookupClientByID(id);
-        if (c == NULL || !(c->flags & CLIENT_TRACKING)) continue;
-        sendTrackingMessage(c,sdskey,sdslen(sdskey));
+        /* Note that if the client is in BCAST mode, we don't want to
+         * send invalidation messages that were pending in the case
+         * previously the client was not in BCAST mode. This can happen if
+         * TRACKING is enabled normally, and then the client switches to
+         * BCAST mode. */
+        if (c == NULL ||
+            !(c->flags & CLIENT_TRACKING)||
+            c->flags & CLIENT_TRACKING_BCAST)
+        {
+            continue;
+        }
+        sendTrackingMessage(c,sdskey,sdslen(sdskey),0);
     }
     raxStop(&ri);
 
@@ -198,7 +317,7 @@ void trackingInvalidateKeysOnFlush(int dbid) {
         while ((ln = listNext(&li)) != NULL) {
             client *c = (client*)listNodeValue(ln);
             if (c->flags & CLIENT_TRACKING) {
-                sendTrackingMessage(c,"",1);
+                sendTrackingMessage(c,"",1,0);
             }
         }
     }
@@ -223,8 +342,8 @@ void trackingInvalidateKeysOnFlush(int dbid) {
 void trackingLimitUsedSlots(void) {
     static unsigned int timeout_counter = 0;
     if (TrackingTable == NULL) return;
-    if (g_pserver->tracking_table_max_fill == 0) return; /* No limits set. */
-    size_t max_keys = g_pserver->tracking_table_max_fill;
+    if (g_pserver->tracking_table_max_keys == 0) return; /* No limits set. */
+    size_t max_keys = g_pserver->tracking_table_max_keys;
     if (raxSize(TrackingTable) <= max_keys) {
         timeout_counter = 0;
         return; /* Limit not reached. */
@@ -259,8 +378,69 @@ void trackingLimitUsedSlots(void) {
     timeout_counter++;
 }
 
+/* This function will run the prefixes of clients in BCAST mode and
+ * keys that were modified about each prefix, and will send the
+ * notifications to each client in each prefix. */
+void trackingBroadcastInvalidationMessages(void) {
+    raxIterator ri, ri2;
+
+    /* Return ASAP if there is nothing to do here. */
+    if (TrackingTable == NULL || !g_pserver->tracking_clients) return;
+
+    raxStart(&ri,PrefixTable);
+    raxSeek(&ri,"^",NULL,0);
+    while(raxNext(&ri)) {
+        bcastState *bs = (bcastState*)ri.data;
+        if (raxSize(bs->keys)) {
+            /* Create the array reply with the list of keys once, then send
+            * it to all the clients subscribed to this prefix. */
+            char buf[32];
+            size_t len = ll2string(buf,sizeof(buf),raxSize(bs->keys));
+            sds proto = sdsempty();
+            proto = sdsMakeRoomFor(proto,raxSize(bs->keys)*15);
+            proto = sdscatlen(proto,"*",1);
+            proto = sdscatlen(proto,buf,len);
+            proto = sdscatlen(proto,"\r\n",2);
+            raxStart(&ri2,bs->keys);
+            raxSeek(&ri2,"^",NULL,0);
+            while(raxNext(&ri2)) {
+                len = ll2string(buf,sizeof(buf),ri2.key_len);
+                proto = sdscatlen(proto,"$",1);
+                proto = sdscatlen(proto,buf,len);
+                proto = sdscatlen(proto,"\r\n",2);
+                proto = sdscatlen(proto,ri2.key,ri2.key_len);
+                proto = sdscatlen(proto,"\r\n",2);
+            }
+            raxStop(&ri2);
+
+            /* Send this array of keys to every client in the list. */
+            raxStart(&ri2,bs->clients);
+            raxSeek(&ri2,"^",NULL,0);
+            while(raxNext(&ri2)) {
+                client *c;
+                memcpy(&c,ri2.key,sizeof(c));
+                sendTrackingMessage(c,proto,sdslen(proto),1);
+            }
+            raxStop(&ri2);
+
+            /* Clean up: we can remove everything from this state, because we
+             * want to only track the new keys that will be accumulated starting
+             * from now. */
+            sdsfree(proto);
+        }
+        raxFree(bs->keys);
+        bs->keys = raxNew();
+    }
+    raxStop(&ri);
+}
+
 /* This is just used in order to access the amount of used slots in the
  * tracking table. */
 uint64_t trackingGetTotalItems(void) {
     return TrackingTableTotalItems;
 }
+
+uint64_t trackingGetTotalKeys(void) {
+    if (TrackingTable == NULL) return 0;
+    return raxSize(TrackingTable);
+}
diff --git a/tests/test_helper.tcl b/tests/test_helper.tcl
index e83f3657a..dfcdb8e35 100644
--- a/tests/test_helper.tcl
+++ b/tests/test_helper.tcl
@@ -92,7 +92,7 @@ set ::file ""; # If set, runs only the tests in this comma separated list
 set ::curfile ""; # Hold the filename of the current suite
 set ::accurate 0; # If true runs fuzz tests with more iterations
 set ::force_failure 0
-set ::timeout 600; # 10 minutes without progresses will quit the test.
+set ::timeout 1200; # 20 minutes without progresses will quit the test.
 set ::last_progress [clock seconds]
 set ::active_servers {} ; # Pids of active Redis instances.
 set ::dont_clean 0
diff --git a/tests/unit/memefficiency.tcl b/tests/unit/memefficiency.tcl
index d152e212c..ec80c7384 100644
--- a/tests/unit/memefficiency.tcl
+++ b/tests/unit/memefficiency.tcl
@@ -209,5 +209,97 @@ start_server {tags {"defrag"}} {
             assert {$digest eq $newdigest}
             r save ;# saving an rdb iterates over all the data / pointers
         } {OK}
+
+        test "Active defrag big list" {
+            r flushdb
+            r config resetstat
+            r config set save "" ;# prevent bgsave from interfereing with save below
+            r config set hz 100
+            r config set activedefrag no
+            r config set active-defrag-max-scan-fields 1000
+            r config set active-defrag-threshold-lower 5
+            r config set active-defrag-cycle-min 65
+            r config set active-defrag-cycle-max 75
+            r config set active-defrag-ignore-bytes 2mb
+            r config set maxmemory 0
+            r config set list-max-ziplist-size 5 ;# list of 500k items will have 100k quicklist nodes
+
+            # create big keys with 10k items
+            set rd [redis_deferring_client]
+
+            set expected_frag 1.7
+            # add a mass of list nodes to two lists (allocations are interlaced)
+            set val [string repeat A 100] ;# 5 items of 100 bytes puts us in the 640 bytes bin, which has 32 regs, so high potential for fragmentation
+            for {set j 0} {$j < 500000} {incr j} {
+                $rd lpush biglist1 $val
+                $rd lpush biglist2 $val
+            }
+            for {set j 0} {$j < 500000} {incr j} {
+                $rd read ; # Discard replies
+                $rd read ; # Discard replies
+            }
+
+            # create some fragmentation
+            r del biglist2
+
+            # start defrag
+            after 120 ;# serverCron only updates the info once in 100ms
+            set frag [s allocator_frag_ratio]
+            if {$::verbose} {
+                puts "frag $frag"
+            }
+
+            assert {$frag >= $expected_frag}
+            r config set latency-monitor-threshold 5
+            r latency reset
+
+            set digest [r debug digest]
+            catch {r config set activedefrag yes} e
+            if {![string match {DISABLED*} $e]} {
+                # wait for the active defrag to start working (decision once a second)
+                wait_for_condition 50 100 {
+                    [s active_defrag_running] ne 0
+                } else {
+                    fail "defrag not started."
+                }
+
+                # wait for the active defrag to stop working
+                wait_for_condition 500 100 {
+                    [s active_defrag_running] eq 0
+                } else {
+                    after 120 ;# serverCron only updates the info once in 100ms
+                    puts [r info memory]
+                    puts [r info stats]
+                    puts [r memory malloc-stats]
+                    fail "defrag didn't stop."
+                }
+
+                # test the the fragmentation is lower
+                after 120 ;# serverCron only updates the info once in 100ms
+                set frag [s allocator_frag_ratio]
+                set max_latency 0
+                foreach event [r latency latest] {
+                    lassign $event eventname time latency max
+                    if {$eventname == "active-defrag-cycle"} {
+                        set max_latency $max
+                    }
+                }
+                if {$::verbose} {
+                    puts "frag $frag"
+                    puts "max latency $max_latency"
+                    puts [r latency latest]
+                    puts [r latency history active-defrag-cycle]
+                }
+                assert {$frag < 1.1}
+                # due to high fragmentation, 100hz, and active-defrag-cycle-max set to 75,
+                # we expect max latency to be not much higher than 7.5ms
+                assert {$max_latency <= 12}
+            }
+            # verify the data isn't corrupted or changed
+            set newdigest [r debug digest]
+            assert {$digest eq $newdigest}
+            r save ;# saving an rdb iterates over all the data / pointers
+            r del biglist1 ;# coverage for quicklistBookmarksClear
+        } {1}
     }
 }
diff --git a/tests/unit/tracking.tcl b/tests/unit/tracking.tcl
new file mode 100644
index 000000000..2058319f7
--- /dev/null
+++ b/tests/unit/tracking.tcl
@@ -0,0 +1,66 @@
+start_server {tags {"tracking"}} {
+    # Create a deferred client we'll use to redirect invalidation
+    # messages to.
+    set rd1 [redis_deferring_client]
+    $rd1 client id
+    set redir [$rd1 read]
+    $rd1 subscribe __redis__:invalidate
+    $rd1 read ; # Consume the SUBSCRIBE reply.
+
+    test {Clients are able to enable tracking and redirect it} {
+        r CLIENT TRACKING on REDIRECT $redir
+    } {*OK}
+
+    test {The other connection is able to get invalidations} {
+        r SET a 1
+        r GET a
+        r INCR a
+        r INCR b ; # This key should not be notified, since it wasn't fetched.
+        set keys [lindex [$rd1 read] 2]
+        assert {[llength $keys] == 1}
+        assert {[lindex $keys 0] eq {a}}
+    }
+
+    test {The client is now able to disable tracking} {
+        # Make sure to add a few more keys in the tracking list
+        # so that we can check for leaks, as a side effect.
+        r MGET a b c d e f g
+        r CLIENT TRACKING off
+    }
+
+    test {Clients can enable the BCAST mode with the empty prefix} {
+        r CLIENT TRACKING on BCAST REDIRECT $redir
+    } {*OK*}
+
+    test {The connection gets invalidation messages about all the keys} {
+        r MSET a 1 b 2 c 3
+        set keys [lsort [lindex [$rd1 read] 2]]
+        assert {$keys eq {a b c}}
+    }
+
+    test {Clients can enable the BCAST mode with prefixes} {
+        r CLIENT TRACKING off
+        r CLIENT TRACKING on BCAST REDIRECT $redir PREFIX a: PREFIX b:
+        r MULTI
+        r INCR a:1
+        r INCR a:2
+        r INCR b:1
+        r INCR b:2
+        r EXEC
+        # Because of the internals, we know we are going to receive
+        # two separated notifications for the two different prefixes.
+        set keys1 [lsort [lindex [$rd1 read] 2]]
+        set keys2 [lsort [lindex [$rd1 read] 2]]
+        set keys [lsort [list {*}$keys1 {*}$keys2]]
+        assert {$keys eq {a:1 a:2 b:1 b:2}}
+    }
+    
+    test {Adding prefixes to BCAST mode works} {
+        r CLIENT TRACKING on BCAST REDIRECT $redir PREFIX c:
+        r INCR c:1234
+        set keys [lsort [lindex [$rd1 read] 2]]
+        assert {$keys eq {c:1234}}
+    }
+
+    $rd1 close
+}
diff --git a/tests/unit/type/stream-cgroups.tcl b/tests/unit/type/stream-cgroups.tcl
index a59e168ef..072ed14d6 100644
--- a/tests/unit/type/stream-cgroups.tcl
+++ b/tests/unit/type/stream-cgroups.tcl
@@ -161,6 +161,15 @@ start_server {
         assert {[$rd read] == {}} ;# before the fix, client didn't even block, but was served synchronously with {mystream {}}
     }
 
+    test {XGROUP DESTROY should unblock XREADGROUP with -NOGROUP} {
+        r del mystream
+        r XGROUP CREATE mystream mygroup $ MKSTREAM
+        set rd [redis_deferring_client]
+        $rd XREADGROUP GROUP mygroup Alice BLOCK 100 STREAMS mystream ">"
+        r XGROUP DESTROY mystream mygroup
+        assert_error "*NOGROUP*" {$rd read}
+    }
+
     test {XCLAIM can claim PEL items from another consumer} {
         # Add 3 items into the stream, and create a consumer group
         r del mystream