diff --git a/README.md b/README.md
index 6770ec1..67874f4 100644
--- a/README.md
+++ b/README.md
@@ -53,10 +53,13 @@ This example fetches the value of the key `foo` and passes it to the
 `var_dump` function. You can use any of the composition provided by
 [promises](https://github.com/reactphp/promise).
 
+If the key `foo` does not exist or when the TTL has passed, the promise will 
+be fulfilled with `null` as value. On any error it will also resolve with `null`.
+
 #### set()
 
 ```php
-$cache->set('foo', 'bar');
+$cache->set('foo', 'bar', 60);
 ```
 
 This example eventually sets the value of the key `foo` to `bar`. If it
diff --git a/src/ArrayCache.php b/src/ArrayCache.php
index 7d6f75f..83f3e34 100644
--- a/src/ArrayCache.php
+++ b/src/ArrayCache.php
@@ -3,11 +3,18 @@
 namespace React\Cache;
 
 use React\Promise;
+use SplPriorityQueue;
 
 class ArrayCache implements CacheInterface
 {
     private $limit;
     private $data = array();
+    private $expires = array();
+
+    /**
+     * @var SplPriorityQueue
+     */
+    private $expiresQueue;
 
     /**
      * The `ArrayCache` provides an in-memory implementation of the [`CacheInterface`](#cacheinterface).
@@ -39,10 +46,16 @@ class ArrayCache implements CacheInterface
     public function __construct($limit = null)
     {
         $this->limit = $limit;
+        $this->expiresQueue = new SplPriorityQueue();
+        $this->expiresQueue->setExtractFlags(SplPriorityQueue::EXTR_BOTH);
     }
 
     public function get($key, $default = null)
     {
+        if (array_key_exists($key, $this->expires)) {
+            $this->garbageCollection();
+        }
+
         if (!array_key_exists($key, $this->data)) {
             return Promise\resolve($default);
         }
@@ -51,28 +64,55 @@ public function get($key, $default = null)
         $value = $this->data[$key];
         unset($this->data[$key]);
         $this->data[$key] = $value;
-
         return Promise\resolve($value);
     }
 
-    public function set($key, $value)
+    public function set($key, $value, $ttl = null)
     {
+        $expires = null;
+
+        if (is_int($ttl)) {
+            $this->expires[$key] = microtime(true) + $ttl;
+            $this->expiresQueue->insert($key, 0 - $this->expires[$key]);
+        }
+
         // unset before setting to ensure this entry will be added to end of array
         unset($this->data[$key]);
         $this->data[$key] = $value;
 
-        // ensure size limit is not exceeded or remove first entry from array
-        if ($this->limit !== null && count($this->data) > $this->limit) {
-            reset($this->data);
-            unset($this->data[key($this->data)]);
-        }
+        $this->garbageCollection();
 
         return Promise\resolve(true);
     }
 
     public function remove($key)
     {
-        unset($this->data[$key]);
+        unset($this->data[$key], $this->expires[$key]);
+        $this->garbageCollection();
         return Promise\resolve(true);
     }
+
+    private function garbageCollection()
+    {
+        // ensure size limit is not exceeded or remove first entry from array
+        while ($this->limit !== null && count($this->data) > $this->limit) {
+            reset($this->data);
+            unset($this->data[key($this->data)]);
+        }
+
+        if ($this->expiresQueue->count() === 0) {
+            return;
+        }
+
+        $this->expiresQueue->rewind();
+        do {
+            $run = false;
+            $item = $this->expiresQueue->current();
+            if ((int)substr((string)$item['priority'], 1) <= microtime(true)) {
+                $this->expiresQueue->extract();
+                $run = true;
+                unset($this->data[$item['data']], $this->expires[$item['data']]);
+            }
+        } while ($run && $this->expiresQueue->count() > 0);
+    }
 }
diff --git a/src/CacheInterface.php b/src/CacheInterface.php
index 3832fac..36968e0 100644
--- a/src/CacheInterface.php
+++ b/src/CacheInterface.php
@@ -34,9 +34,10 @@ public function get($key, $default = null);
      *
      * @param string $key
      * @param mixed $value
+     * @param float|null $ttl
      * @return PromiseInterface Returns a promise which resolves to true on success of false on error
      */
-    public function set($key, $value);
+    public function set($key, $value, $ttl = null);
 
     /**
      * Remove an item from the cache, returns a promise which resolves to true on success or
diff --git a/tests/ArrayCacheTest.php b/tests/ArrayCacheTest.php
index bacf448..4134711 100644
--- a/tests/ArrayCacheTest.php
+++ b/tests/ArrayCacheTest.php
@@ -152,4 +152,47 @@ public function testGetWithLimitedSizeWillUpdateLRUInfo()
         $this->cache->get('bar')->then($this->expectCallableOnceWith(null));
         $this->cache->get('baz')->then($this->expectCallableOnceWith('3'));
     }
+
+    /** @test */
+    public function getWithinTtl()
+    {
+        $this->cache
+            ->set('foo', 'bar', 100);
+
+
+        $success = $this->createCallableMock();
+        $success
+            ->expects($this->once())
+            ->method('__invoke')
+            ->with('bar');
+
+        $this->cache
+            ->get('foo')
+            ->then(
+                $success,
+                $this->expectCallableNever()
+            );
+    }
+
+    /** @test */
+    public function getAfterTtl()
+    {
+        $this->cache
+            ->set('foo', 'bar', 1);
+
+        sleep(2);
+
+        $success = $this->createCallableMock();
+        $success
+            ->expects($this->once())
+            ->method('__invoke')
+            ->with(null);
+
+        $this->cache
+            ->get('foo')
+            ->then(
+                $success,
+                $this->expectCallableNever()
+            );
+    }
 }