diff --git a/src/categories.js b/src/categories.js
index 11c86e81fd..713ce64220 100644
--- a/src/categories.js
+++ b/src/categories.js
@@ -317,8 +317,6 @@ var db = require('./database'),
 			if(parseInt(topicData.pinned, 10) === 0) {
 				db.sortedSetAdd('categories:' + cid + ':tid', postData.timestamp, postData.tid);
 			}
-
-			Categories.addActiveUser(cid, postData.uid, postData.timestamp);
 		});
 	};
 
diff --git a/src/categories/activeusers.js b/src/categories/activeusers.js
index 9b8e558aae..57873944b8 100644
--- a/src/categories/activeusers.js
+++ b/src/categories/activeusers.js
@@ -1,83 +1,31 @@
 'use strict';
 
 var async = require('async'),
-
 	db = require('./../database'),
 	posts = require('./../posts'),
 	topics = require('./../topics');
 
 module.exports = function(Categories) {
 
-	Categories.isUserActiveIn = function(cid, uid, callback) {
-
-		db.getSortedSetRange('uid:' + uid + ':posts', 0, -1, function(err, pids) {
-			if (err) {
-				return callback(err);
-			}
-
-			var index = 0,
-				active = false;
-
-			async.whilst(
-				function() {
-					return active === false && index < pids.length;
-				},
-				function(callback) {
-					posts.getCidByPid(pids[index], function(err, postCid) {
-						if (err) {
-							return callback(err);
-						}
-
-						if (postCid === cid) {
-							active = true;
-						}
+	Categories.getActiveUsers = function(cid, callback) {
+		db.getSortedSetRevRange('categories:recent_posts:cid:' + cid, 0, 99, function(err, pids) {
+			var keys = pids.map(function(pid) {
+				return 'post:' + pid;
+			});
 
-						++index;
-						callback();
-					});
-				},
-				function(err) {
-					callback(err, active);
+			db.getObjectsFields(keys, ['uid'], function(err, users) {
+				if (err) {
+					return callback(err);
 				}
-			);
-		});
-	};
 
-	Categories.addActiveUser = function(cid, uid, timestamp) {
-		if(parseInt(uid, 10)) {
-			db.sortedSetAdd('cid:' + cid + ':active_users', timestamp, uid);
-		}
-	};
-
-	Categories.removeActiveUser = function(cid, uid, callback) {
-		db.sortedSetRemove('cid:' + cid + ':active_users', uid, callback);
-	};
+				var uids = users.map(function(user) {
+					return user.uid;
+				}).filter(function(value, index, array) {
+					return parseInt(value, 10) !== 0 && array.indexOf(value) === index;
+				}).slice(0, 24);
 
-	Categories.getActiveUsers = function(cid, callback) {
-		db.getSortedSetRevRange('cid:' + cid + ':active_users', 0, 23, callback);
-	};
-
-	Categories.moveActiveUsers = function(tid, oldCid, cid) {
-		function updateUser(uid, timestamp) {
-			Categories.addActiveUser(cid, uid, timestamp);
-			Categories.isUserActiveIn(oldCid, uid, function(err, active) {
-
-				if (!err && !active) {
-					Categories.removeActiveUser(oldCid, uid);
-				}
+				callback(null, uids);
 			});
-		}
-
-		topics.getTopicField(tid, 'timestamp', function(err, timestamp) {
-			if(!err) {
-				topics.getUids(tid, function(err, uids) {
-					if (!err && uids) {
-						for (var i = 0; i < uids.length; ++i) {
-							updateUser(uids[i], timestamp);
-						}
-					}
-				});
-			}
 		});
 	};
 };
diff --git a/src/categories/recentreplies.js b/src/categories/recentreplies.js
index 33ee629811..925e83e42e 100644
--- a/src/categories/recentreplies.js
+++ b/src/categories/recentreplies.js
@@ -2,6 +2,8 @@
 'use strict';
 
 var async = require('async'),
+	winston = require('winston'),
+
 	db = require('./../database'),
 	posts = require('./../posts'),
 	topics = require('./../topics'),
@@ -23,26 +25,40 @@ module.exports = function(Categories) {
 	};
 
 	Categories.moveRecentReplies = function(tid, oldCid, cid) {
-		function movePost(pid, next) {
-			posts.getPostField(pid, 'timestamp', function(err, timestamp) {
-				if(err) {
-					return next(err);
+		function movePost(postData, next) {
+			async.parallel([
+				function(next) {
+					db.sortedSetRemove('categories:recent_posts:cid:' + oldCid, postData.pid, next);
+				},
+				function(next) {
+					db.sortedSetAdd('categories:recent_posts:cid:' + cid, postData.timestamp, postData.pid, next);
 				}
-
-				db.sortedSetRemove('categories:recent_posts:cid:' + oldCid, pid);
-				db.sortedSetAdd('categories:recent_posts:cid:' + cid, timestamp, pid);
-				next();
-			});
+			], next);
 		}
 
 		topics.getPids(tid, function(err, pids) {
-			if(!err && pids) {
-				async.each(pids, movePost, function(err) {
+			if (err) {
+				return winston.error(err.message);
+			}
+			if (pids && !pids.length) {
+				return;
+			}
+
+			var keys = pids.map(function(pid) {
+				return 'post:' + pid;
+			});
+
+			db.getObjectsFields(keys, ['pid', 'timestamp'], function(err, postData) {
+				if (err) {
+					return winston.error(err.message);
+				}
+
+				async.each(postData, movePost, function(err) {
 					if (err) {
 						winston.error(err.message);
 					}
 				});
-			}
+			});
 		});
 	};
 };
diff --git a/src/threadTools.js b/src/threadTools.js
index 55bac851b4..63a29cf95d 100644
--- a/src/threadTools.js
+++ b/src/threadTools.js
@@ -201,8 +201,6 @@ var winston = require('winston'),
 				categories.incrementCategoryFieldBy(cid, 'topic_count', 1);
 			}
 
-			categories.moveActiveUsers(tid, oldCid, cid);
-
 			categories.moveRecentReplies(tid, oldCid, cid);
 
 			topics.setTopicField(tid, 'cid', cid, callback);
diff --git a/src/user/delete.js b/src/user/delete.js
index c7e4ae1169..33f0f8d10e 100644
--- a/src/user/delete.js
+++ b/src/user/delete.js
@@ -266,9 +266,6 @@ module.exports = function(User) {
 				function(next) {
 					db.delete('uid:' + uid + ':downvote', next);
 				},
-				function(next) {
-					deleteUserFromCategoryActiveUsers(uid, next);
-				},
 				function(next) {
 					deleteUserFromFollowers(uid, next);
 				},
@@ -298,18 +295,6 @@ module.exports = function(User) {
 		});
 	}
 
-	function deleteUserFromCategoryActiveUsers(uid, callback) {
-		db.getSortedSetRange('categories:cid', 0, -1, function(err, cids) {
-			if (err) {
-				return callback(err);
-			}
-
-			async.each(cids, function(cid, next) {
-				categories.removeActiveUser(cid, uid, next);
-			}, callback);
-		});
-	}
-
 	function deleteUserFromFollowers(uid, callback) {
 		db.getSetMembers('followers:' + uid, function(err, uids) {
 			if (err) {