diff --git a/app.js b/app.js
index a8eb5bd..7ac8114 100644
--- a/app.js
+++ b/app.js
@@ -1,5 +1,6 @@
 let fs = require('fs'),
-    path = require('path');
+    path = require('path'),
+    util = require('util');
 const serializejs = require('serialize-javascript');
 
 const commandLineArgs = require('command-line-args');
@@ -81,6 +82,15 @@ global.syzoj = {
     if (!module.parent) {
       await this.lib('judger').connect();
     }
+
+    // redis and redisCache is for syzoj-renderer
+    const redis = require('redis');
+    this.redis = redis.createClient(this.config.redis);
+    this.redisCache = {
+      get: util.promisify(this.redis.get).bind(this.redis),
+      set: util.promisify(this.redis.set).bind(this.redis)
+    };
+
     this.loadModules();
   },
   async connectDatabase() {
diff --git a/config-example.json b/config-example.json
index 72a8afc..ba7bcc8 100644
--- a/config-example.json
+++ b/config-example.json
@@ -111,6 +111,7 @@
   ],
   "session_secret": "@SESSION_SECRET@",
   "rabbitMQ": "amqp://localhost/",
+  "redis": "redis://127.0.0.1:6379",
   "email_jwt_secret": "@EMAIL_JWT_SECRET@",
   "google_analytics": "UA-XXXXXXXX-X",
   "gravatar_url": "https://cdn.v2ex.com/gravatar",
diff --git a/libs/highlight.js b/libs/highlight.js
index 0239a35..e6feca5 100644
--- a/libs/highlight.js
+++ b/libs/highlight.js
@@ -1,5 +1,6 @@
 const { highlight } = require('syzoj-renderer');
+const objectHash = require('object-hash');
 
-module.exports = (code, lang, cb) => {
-  highlight(code, lang).then(cb);
+module.exports = async (code, lang, cb) => {
+  highlight(code, lang, syzoj.redisCache).then(cb);
 }
diff --git a/libs/markdown.js b/libs/markdown.js
index 3618d76..0666363 100644
--- a/libs/markdown.js
+++ b/libs/markdown.js
@@ -20,16 +20,6 @@ const xss = new XSS.FilterXSS({
   }
 });
 
-const defaultCache = {
-    data: {},
-    get(key) {
-        return this.data[key];
-    },
-    set(key, val) {
-        this.data[key] = val;
-    }
-};
-
 function filter(html) {
   html = xss.process(html);
   if (html) {
@@ -39,5 +29,5 @@ function filter(html) {
 };
 
 module.exports = (markdownCode, callback) => {
-  markdown(markdownCode, defaultCache, filter).then(callback);
+  markdown(markdownCode, syzoj.redisCache, filter).then(callback);
 };
diff --git a/package.json b/package.json
index b9fce8f..2ae48e6 100644
--- a/package.json
+++ b/package.json
@@ -49,7 +49,9 @@
     "node-7z": "^0.4.0",
     "nodemailer": "^4.7.0",
     "object-assign-deep": "^0.4.0",
+    "object-hash": "^1.3.1",
     "randomstring": "^1.1.5",
+    "redis": "^2.8.0",
     "request": "^2.74.0",
     "request-promise": "^4.1.1",
     "sendmail": "^1.1.1",