diff --git a/persistence.js b/persistence.js
index b239691..79da086 100644
--- a/persistence.js
+++ b/persistence.js
@@ -7,7 +7,8 @@ var Packet = require('aedes-packet')
 var QlobberOpts = {
   wildcard_one: '+',
   wildcard_some: '#',
-  separator: '/'
+  separator: '/',
+  match_empty_levels: true
 }
 
 function MemoryPersistence () {
@@ -18,8 +19,10 @@ function MemoryPersistence () {
   this._retained = []
   // clientId -> topic -> qos
   this._subscriptions = new Map()
+  this._sharedSubscriptions = new Map()
   this._clientsCount = 0
   this._trie = new QlobberSub(QlobberOpts)
+  this._trieShared = new QlobberSub(QlobberOpts)
   this._outgoing = {}
   this._incoming = {}
   this._wills = {}
@@ -103,6 +106,42 @@ MemoryPersistence.prototype.addSubscriptions = function (client, subs, cb) {
   cb(null, client)
 }
 
+MemoryPersistence.prototype.addSharedSubscription = function (client, sub, cb) {
+  var stored = this._sharedSubscriptions.get(client.id)
+  var trie = this._trieShared
+
+  if (!stored) {
+    stored = new Map()
+    this._sharedSubscriptions.set(client.id, stored)
+  }
+
+  trie.add(sub.topic, {
+    clientId: client.id,
+    topic: sub.topic,
+    qos: sub.qos
+  })
+
+  stored.set(sub.topic, { qos: sub.qos, lastUpdate: 0 })
+
+  cb(null, client)
+}
+
+MemoryPersistence.prototype.removeSharedSubscription = function (client, topic, cb) {
+  var stored = this._sharedSubscriptions.get(client.id)
+  var trie = this._trieShared
+
+  if (stored) {
+    trie.remove(topic, { clientId: client.id, topic: topic })
+    stored.delete(topic)
+  }
+
+  if (stored.size === 0) {
+    this._sharedSubscriptions.delete(client.id)
+  }
+
+  cb(null, client)
+}
+
 MemoryPersistence.prototype.removeSubscriptions = function (client, subs, cb) {
   var stored = this._subscriptions.get(client.id)
   var trie = this._trie
@@ -148,6 +187,41 @@ MemoryPersistence.prototype.subscriptionsByTopic = function (pattern, cb) {
   cb(null, this._trie.match(pattern))
 }
 
+MemoryPersistence.prototype.nextSharedSubscription = function (topic, group, cb) {
+  var subs = this._trieShared.match('$share/' + group + '/' + topic)
+  var stored = this._sharedSubscriptions
+
+  var sub = null
+  for (let i = 0, len = subs.length; i < len; i++) {
+    var s = stored.get(subs[i].clientId)
+    if (!s || !s.get(subs[i].topic)) continue
+    s = s.get(subs[i].topic)
+
+    if (s.lastUpdate === 0) {
+      sub = subs[i]
+      break
+    } else if (s.lastUpdate < sub.lastUpdate) {
+      sub = subs[i]
+    }
+  }
+  cb(null, sub)
+}
+
+MemoryPersistence.prototype.updateSharedSubscription = function (client, topic, group, cb) {
+  var stored = this._sharedSubscriptions.get(client.id)
+  topic = '$share/' + group + '/' + topic
+
+  if (stored) {
+    var sub = stored.get(topic)
+
+    if (sub) {
+      sub.lastUpdate = Date.now()
+    }
+  }
+
+  cb(null)
+}
+
 MemoryPersistence.prototype.cleanSubscriptions = function (client, cb) {
   var trie = this._trie
   var stored = this._subscriptions.get(client.id)