diff --git a/index.js b/index.js
index cb1a12e..b64dd5a 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,7 @@ var _ = require('underscore');
 exports.setup = function(server, client, options) {
   var self = this;
 
-  self.engine = options.engine || RedisEngine.create(options.servers);
+  self.engine = options.engine || RedisEngine.create(server, options.servers);
   self.channelRe = options.channelRe || /^\/presence\//;
 
   server.addExtension({
diff --git a/lib/redis_engine.js b/lib/redis_engine.js
index e79d6d0..6039e03 100644
--- a/lib/redis_engine.js
+++ b/lib/redis_engine.js
@@ -1,26 +1,75 @@
 var ShardManager = require('shard-manager');
 var redis = require('redis');
+var Shavaluator = require('redis-evalsha');
 var _ = require('underscore');
 
-var RedisEngine = function(addresses) {
+var RedisEngine = function(server, addresses) {
   var shards = _.map(addresses, function(address, index) {
     var components = address.split(':');
     var hostname = components[0];
     var port = components[1];
 
+    var client = redis.createClient(port, hostname);
+    var evalsha = new Shavaluator(client);
+
+    /*
+      ARGV[1] = clientId
+      ARGV[2] = data
+      ARGV[3] = presenceId
+      ARGV[4] = currentDate
+      KEYS[1] = data
+      KEYS[2] = pid
+      KEYS[3] = cids
+      KEYS[4] = pids
+    */
+    evalsha.add('subscribe_presence', `
+      local exists = redis.call('EXISTS', KEYS[1])
+
+      redis.call('SET', KEYS[1], ARGV[2])
+      redis.call('SET', KEYS[2], ARGV[3])
+      redis.call('ZADD', KEYS[3], ARGV[4], ARGV[1])
+      redis.call('ZADD', KEYS[4], ARGV[4], ARGV[3])
+
+      return exists
+    `);
+
+    /*
+      ARGV[1] = clientId
+      ARGV[2] = presenceId
+      KEYS[1] = data
+      KEYS[2] = pid
+      KEYS[3] = cids
+      KEYS[4] = pids
+    */
+    evalsha.add('unsubscribe_presence', `
+      redis.call('DEL', KEYS[2])
+      redis.call('ZREM', KEYS[3], ARGV[1])
+
+      if redis.call('EXISTS', KEYS[3]) == 1 then
+        return 1
+      end
+
+      redis.call('ZREM', KEYS[4], ARGV[2])
+      redis.call('DEL', KEYS[1])
+
+      return 0
+    `);
+
     return {
       shardName: 'node' + index,
       shard: {
-        redis: redis.createClient(port, hostname)
+        evalsha: evalsha,
+        redis: client
       }
     };
   });
 
+  this._server = server._server;
   this._shardManager = new ShardManager(shards);
 }
 
-RedisEngine.create = function(server, options) {
-  return new RedisEngine(server, options);
+RedisEngine.create = function(server, addresses, options) {
+  return new RedisEngine(server, addresses, options);
 }
 
 function key() {
@@ -64,29 +113,50 @@ RedisEngine.prototype = {
     // ZADD cids:$channel:$presenceId $now $clientId
     // ZADD pids:$channel $now $presenceId
     var self = this;
-    var client = self._shardManager.getShard(channel).redis;
 
-    var isNew = true;
+    self._server.debug('Registering client ? for presence channel ? ?', clientId, channel, presenceId);
 
-    client.multi()
-      .exists(key('data', channel, presenceId), function(err, exists) {
-        if (exists == 1) {
-          isNew = false;
-        }
-      })
-      .set(key('data', channel, presenceId), data)
-      .set(key('pid', channel, clientId), presenceId)
-      .zadd(key('cids', channel, presenceId), Date.now(), clientId)
-      .zadd(key('pids', channel), Date.now(), presenceId)
-      .exec(function(err) {
-        if (err) {
-          console.log('redis error: ', err);
-          done(err);
-          return;
-        }
+    self._server._engine.clientExists(clientId, function (existsResult) {
+      if(!existsResult) {
+        self._server.debug('Will not register client ? for presence channel ? ?', clientId, channel, presenceId);
+
+        return;
+      }
 
-        done(null, isNew);
+      self._shardManager.getShard(channel).evalsha.exec('subscribe_presence', [
+        key('data', channel, presenceId),
+        key('pid', channel, clientId),
+        key('cids', channel, presenceId),
+        key('pids', channel),
+      ], [
+        clientId,
+        data,
+        presenceId,
+        Date.now(),
+      ], function (err, results) {
+        self._server._engine.clientExists(clientId, function (existsResult) {
+          if(!existsResult) {
+            self._server.debug('Client ? disappeared while registering for presence channel ? ?', clientId, channel, presenceId);
+
+            self.unsubscribe(channel, clientId);
+
+            done(null, false);
+
+            return;
+          } else if(results === 1) {
+            self._server.debug('Registered new client ? for presence channel ? ? ?', clientId, channel, presenceId);
+
+            done(null, false);
+          } else if(results === 0) {
+            self._server.debug('Registered initial client ? for presence channel ? ? ?', clientId, channel, presenceId);
+
+            done(null, true);
+          } else {
+            self._server.debug('Failed to register client ? for presence channel ? ? ? ?', clientId, channel, presenceId, err, results);
+          }
+        });
       });
+    });
   },
 
   getSubscribers: function(channel, done) {
@@ -203,51 +273,35 @@ RedisEngine.prototype = {
     var client = self._shardManager.getShard(channel).redis;
 
     client.get(key('pid', channel, clientId), function(err, presenceId) {
-      if (err) {
-        console.log('error loading client presenceId', err);
-        done(err);
+      if(presenceId === null) {
+        self._server.debug('Will not deregister client ? for presence channel ? ?', clientId, channel, presenceId);
+
         return;
       }
 
-      var isLast = false;
-
-      client.multi()
-        .del(key('pid', channel, clientId), channel)
-        .zrem(key('cids', channel, presenceId), clientId)
-        .exists(key('cids', channel, presenceId), function(err, exists) {
-          if (err) {
-            console.log('error removing client subscription', err);
-            return;
-          }
-
-          if (exists == 0) {
-            isLast = true;
-          }
-        })
-        .exec(function(err) {
-          if (err) {
-            console.log('error removing client subscription', err);
-            done(err);
-            return;
-          }
-
-          if (!isLast) {
-            done(null, presenceId, false);
-          } else {
-            client.multi()
-              .zrem(key('pids', channel), presenceId)
-              .del(key('data', channel, presenceId))
-              .exec(function(err) {
-                if (err) {
-                  console.log('error removing client subscription', err);
-                  done(err);
-                  return;
-                }
-
-                done(null, presenceId, true);
-              });
-          }
-        });
+      self._server.debug('Deregistering client ? for presence channel ? ?', clientId, channel, presenceId);
+
+      self._shardManager.getShard(channel).evalsha.exec('unsubscribe_presence', [
+        key('data', channel, presenceId),
+        key('pid', channel, clientId),
+        key('cids', channel, presenceId),
+        key('pids', channel),
+      ], [
+        clientId,
+        presenceId,
+      ], function (err, results) {
+        if(results === 1) {
+          self._server.debug('Deregistered client ? for presence channel ? ?', clientId, channel, presenceId);
+
+          if(done) done(null, presenceId, false);
+        } else if(results === 0) {
+          self._server.debug('Deregistered final client ? for presence channel ? ?', clientId, channel, presenceId);
+
+          if(done) done(null, presenceId, true);
+        } else {
+          self._server.debug('Failed to deregister client ? for presence channel ? ? ? ?', clientId, channel, presenceId, err, results);
+        }
+      });
     });
   }
 };