diff --git a/src/categories.js b/src/categories.js
index ba772bb5c1..24efbc4f16 100644
--- a/src/categories.js
+++ b/src/categories.js
@@ -217,13 +217,7 @@ var db = require('./database'),
 	};
 
 	Categories.hasReadCategory = function(cid, uid, callback) {
-		db.isSetMember('cid:' + cid + ':read_by_uid', uid, function(err, hasRead) {
-			if(err) {
-				return callback(false);
-			}
-
-			callback(hasRead);
-		});
+		db.isSetMember('cid:' + cid + ':read_by_uid', uid, callback);
 	};
 
 	Categories.getRecentReplies = function(cid, uid, count, callback) {
diff --git a/src/database/mongo.js b/src/database/mongo.js
index 92a80cebf7..8c2d527309 100644
--- a/src/database/mongo.js
+++ b/src/database/mongo.js
@@ -469,6 +469,24 @@
 		});
 	};
 
+	module.isSetMembers = function(key, values, callback) {
+		for (var i=0; i<values.length; ++i) {
+			values[i] = toString(values[i]);
+		}
+
+		db.collection('objects').findOne({_key:key, members: {$in : values}}, function(err, items) {
+			if (err) {
+				return callback(err);
+			}
+
+			values = values.map(function(value) {
+				return items.members.indexOf(value) !== -1
+			});
+
+			callback(null, values);
+		});
+	};
+
 	module.isMemberOfSets = function(sets, value, callback) {
 
 		value = toString(value);
diff --git a/src/database/redis.js b/src/database/redis.js
index a0235e4b67..1c6a4d4f27 100644
--- a/src/database/redis.js
+++ b/src/database/redis.js
@@ -305,14 +305,32 @@
 		});
 	};
 
+	module.isSetMembers = function(key, values, callback) {
+		var multi = redisClient.multi();
+		for (var i=0; i<values.length; ++i) {
+			multi.sismember(key, values[i]);
+		}
+
+		multi.exec(function(err, results) {
+			if (err) {
+				return callback(err);
+			}
+
+			for (var i=0; i<results.length; ++i) {
+				results[i] = results[i] === 1;
+			}
+			callback(null, results);
+		});
+	};
+
 	module.isMemberOfSets = function(sets, value, callback) {
-		var batch = redisClient.multi();
+		var multi = redisClient.multi();
 
 		for (var i = 0, ii = sets.length; i < ii; i++) {
-			batch.sismember(sets[i], value);
+			multi.sismember(sets[i], value);
 		}
 
-		batch.exec(callback);
+		multi.exec(callback);
 	};
 
 	module.getSetMembers = function(key, callback) {