diff --git a/lib/history.js b/lib/history.js
index 4a3bbe1..bdc922d 100644
--- a/lib/history.js
+++ b/lib/history.js
@@ -2,6 +2,7 @@
 //external modules
 var async = require('async');
 var moment = require('moment');
+var childProcess = require('child_process');
 
 //core
 var config = require("./config.js");
@@ -9,6 +10,9 @@ var logger = require("./logger.js");
 var response = require("./response.js");
 var models = require("./models");
 
+// workers
+var historyUpdater = require("./workers/historyUpdater");
+
 //public
 var History = {
     historyGet: historyGet,
@@ -20,49 +24,50 @@ var History = {
 
 var caches = {};
 //update when the history is dirty
+var updaterIsBusy = false;
 var updater = setInterval(function () {
+    if (updaterIsBusy) return;
     var deleted = [];
-    async.each(Object.keys(caches), function (key, callback) {
+    var _caches = {};
+    Object.keys(caches).forEach(function (key) {
         var cache = caches[key];
         if (cache.isDirty) {
-            if (config.debug) logger.info("history updater found dirty history: " + key);
-            var history = parseHistoryToArray(cache.history);
-            finishUpdateHistory(key, history, function (err, count) {
-                if (err) return callback(err, null);
-                if (!count) return callback(null, null);
-                cache.isDirty = false;
-                cache.updateAt = Date.now();
-                return callback(null, null);
-            });
+            _caches[key] = cache.history;
+            cache.isDirty = false;
         } else {
             if (moment().isAfter(moment(cache.updateAt).add(5, 'minutes'))) {
                 deleted.push(key);
             }
-            return callback(null, null);
         }
-    }, function (err) {
-        if (err) return logger.error('history updater error', err);
     });
     // delete specified caches
     for (var i = 0, l = deleted.length; i < l; i++) {
         caches[deleted[i]].history = {};
         delete caches[deleted[i]];
     }
-}, 1000);
-
-function finishUpdateHistory(userid, history, callback) {
-    models.User.update({
-        history: JSON.stringify(history)
-    }, {
-        where: {
-            id: userid
-        }
-    }).then(function (count) {
-        return callback(null, count);
-    }).catch(function (err) {
-        return callback(err, null);
+    if (Object.keys(_caches).length <= 0) return;
+    updaterIsBusy = true;
+    var worker = childProcess.fork("./lib/workers/historyUpdater.js");
+    if (config.debug) logger.info('history updater worker process started');
+    worker.send({
+        msg: 'update history',
+        caches: _caches
     });
-}
+    worker.on('message', function (data) {
+        if (!data || !data.msg || !data.userid) return;
+        var cache = caches[data.userid];
+        if (!cache) return;
+        switch(data.msg) {
+            case 'check':
+                cache.updateAt = Date.now();
+                break;
+        }
+    });
+    worker.on('close', function (code) {
+        updaterIsBusy = false;
+        if (config.debug) logger.info('history updater worker process exited with code ' + code);
+    });
+}, 1000);
 
 function isReady() {
     var dirtyCount = 0;
@@ -101,7 +106,7 @@ function getHistory(userid, callback) {
 }
 
 function setHistory(userid, history) {
-    if (Array.isArray(history)) history = parseHistoryToObject(history);
+    if (Array.isArray(history)) history = historyUpdater.parseHistoryToObject(history);
     if (!caches[userid]) {
         caches[userid] = {
             history: {},
@@ -130,31 +135,13 @@ function updateHistory(userid, noteId, document) {
     }
 }
 
-function parseHistoryToArray(history) {
-    var _history = [];
-    Object.keys(history).forEach(function (key) {
-        var item = history[key];
-        _history.push(item);
-    });
-    return _history;
-}
-
-function parseHistoryToObject(history) {
-    var _history = {};
-    for (var i = 0, l = history.length; i < l; i++) {
-        var item = history[i];
-        _history[item.id] = item;
-    }
-    return _history;
-}
-
 function historyGet(req, res) {
     if (req.isAuthenticated()) {
         getHistory(req.user.id, function (err, history) {
             if (err) return response.errorInternalError(res);
             if (!history) return response.errorNotFound(res);
             res.send({
-                history: parseHistoryToArray(history)
+                history: historyUpdater.parseHistoryToArray(history)
             });
         });
     } else {
diff --git a/lib/workers/historyUpdater.js b/lib/workers/historyUpdater.js
new file mode 100644
index 0000000..df80e92
--- /dev/null
+++ b/lib/workers/historyUpdater.js
@@ -0,0 +1,66 @@
+// external modules
+var async = require('async');
+
+// core
+var config = require("../config.js");
+var logger = require("../logger.js");
+var models = require("../models");
+
+process.on('message', function (data) {
+    if (!data || !data.msg || data.msg !== 'update history' || !data.caches) return process.exit();
+    var caches = data.caches;
+    async.each(Object.keys(caches), function (key, callback) {
+        var cache = caches[key];
+        if (config.debug) logger.info("history updater found dirty history: " + key);
+        var history = parseHistoryToArray(cache);
+        finishUpdateHistory(key, history, function (err, count) {
+            if (err) return callback(err, null);
+            if (!count) return callback(null, null);
+            process.send({
+                msg: 'check',
+                userid: key
+            });
+            return callback(null, null);
+        });
+    }, function (err) {
+        if (err) logger.error('history updater error', err);
+        process.exit();
+    });
+});
+
+function finishUpdateHistory(userid, history, callback) {
+    models.User.update({
+        history: JSON.stringify(history)
+    }, {
+        where: {
+            id: userid
+        }
+    }).then(function (count) {
+        return callback(null, count);
+    }).catch(function (err) {
+        return callback(err, null);
+    });
+}
+
+function parseHistoryToArray(history) {
+    var _history = [];
+    Object.keys(history).forEach(function (key) {
+        var item = history[key];
+        _history.push(item);
+    });
+    return _history;
+}
+
+function parseHistoryToObject(history) {
+    var _history = {};
+    for (var i = 0, l = history.length; i < l; i++) {
+        var item = history[i];
+        _history[item.id] = item;
+    }
+    return _history;
+}
+
+module.exports = {
+    parseHistoryToArray: parseHistoryToArray,
+    parseHistoryToObject: parseHistoryToObject
+};
\ No newline at end of file