diff --git a/django/contrib/sessions/backends/cached_db.py b/django/contrib/sessions/backends/cached_db.py
index 580e907c30..342aa600d3 100644
--- a/django/contrib/sessions/backends/cached_db.py
+++ b/django/contrib/sessions/backends/cached_db.py
@@ -28,6 +28,8 @@ class SessionStore(DBStore):
         return data
 
     def exists(self, session_key):
+        if (KEY_PREFIX + session_key) in cache:
+            return True
         return super(SessionStore, self).exists(session_key)
 
     def save(self, must_create=False):
diff --git a/django/contrib/sessions/tests.py b/django/contrib/sessions/tests.py
index f94753cbcf..50297dce2f 100644
--- a/django/contrib/sessions/tests.py
+++ b/django/contrib/sessions/tests.py
@@ -293,6 +293,11 @@ class CacheDBSessionTests(SessionTestsMixin, TestCase):
 
     backend = CacheDBSession
 
+    def test_exists_searches_cache_first(self):
+        self.session.save()
+        with self.assertNumQueries(0):
+            self.assertTrue(self.session.exists(self.session.session_key))
+
 
 CacheDBSessionWithTimeZoneTests = override_settings(USE_TZ=True)(CacheDBSessionTests)