diff --git a/.jshintrc b/.jshintrc
index 08a8bed..5780e54 100644
--- a/.jshintrc
+++ b/.jshintrc
@@ -3,7 +3,7 @@
   "curly": true,
   "eqeqeq": true,
   "es3": false,
-  "forin": false,
+  "forin": true,
   "freeze": true,
   "immed": false,
   "indent": 2,
@@ -26,5 +26,6 @@
   "maxlen": 80,
   "node": true,
   "browser": false,
-  "esnext": true
+  "esnext": true,
+  "sub": true
 }
diff --git a/config/default.yml b/config/default.yml
index b2ffca1..b21ba4d 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -15,3 +15,16 @@ pac:
 gzip:
   # Compression level for gzip.
   level: 9
+
+# Cache configuration.
+cache:
+  # Enable cache. Don't rename it to 'enabled' as this will crash the parser.
+  use: true
+  # Supported cache types are:
+  # - basic (in-memory JS)
+  # - redis (requires Redis database)
+  type: basic
+  # Configuration for non-basic database server.
+  database:
+    host: localhost
+    port: 55255
diff --git a/lib/cache.js b/lib/cache.js
new file mode 100644
index 0000000..60a070a
--- /dev/null
+++ b/lib/cache.js
@@ -0,0 +1,41 @@
+var storage = require('./storage');
+
+var DEF_MAX_SIZE = 3000;
+
+// Resource caching interface, creates a new storage.
+var Cache = function(options) {
+  this.maxSize = options.maxCacheSize || DEF_MAX_SIZE;
+  this.storage = storage.create(options.cache.type);
+};
+Cache.prototype.save = function(key, value, expire) {
+  this.storage.save(key, value, expire);
+};
+Cache.prototype.load = function(key, callback) {
+  this.storage.load(key, callback);
+};
+
+// Default cache instance.
+var instance = null;
+
+// Initializes a new cache for given storage type.
+exports.init = function(options) {
+  if (options.cache.use) {
+    instance = new Cache(options);
+  }
+};
+
+// Saves new cache entry.
+exports.save = function(key, value, expire) {
+  if (instance) {
+    instance.save(key, value, expire);
+  }
+};
+
+// Returns cache entry for given key if available.
+exports.load = function(key, callback) {
+  if (instance) {
+    instance.load(key, callback);
+  } else {
+    callback();
+  }
+};
diff --git a/lib/index.js b/lib/index.js
index 7fc2642..a38d0af 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -38,7 +38,6 @@ function addVersionConfig() {
 CONFIG.getConfigSources().forEach(function(config) {
   addVersionConfig();
   console.log('Using configuration %s:', config.name);
-  console.dir(config.parsed);
 });
 
 var SpdyProxy = require('./proxy');
diff --git a/lib/plugins/cacheload.js b/lib/plugins/cacheload.js
new file mode 100644
index 0000000..ccb7602
--- /dev/null
+++ b/lib/plugins/cacheload.js
@@ -0,0 +1,22 @@
+var url = require('url');
+var cache = require('../cache');
+
+exports.load = function(request, dest, options, callback) {
+  if (!options.cache.use || request.method !== 'GET') {
+    // Do nothing for POST and CONNECT requests or when caching is disabled.
+    callback(null, false);
+  }
+
+  var path = request.headers.path || url.parse(request.url).path;
+  var key = [request.headers.host, path];
+  cache.load(key, function(error, cached) {
+    if (!error && cached) {
+      var value = cached.value;
+      request.log('delivering %d bytes from cache', cached.size);
+      dest.writeHead(value[0][0], value[0][1], value[0][2]);
+      // TODO(esawin): fix explicit buffer creation workaround for redis.
+      dest.end(new Buffer(value[1]));
+    }
+    callback(error, Boolean(cached));
+  });
+};
diff --git a/lib/plugins/cachesave.js b/lib/plugins/cachesave.js
new file mode 100644
index 0000000..7ee5210
--- /dev/null
+++ b/lib/plugins/cachesave.js
@@ -0,0 +1,86 @@
+var url = require('url');
+var cache = require('../cache');
+
+var MAX_EXPIRE = 7 * 24 * 60 * 60;
+// var DEF_EXPIRE = 1 * 24 * 60 * 60;
+var DEF_EXPIRE = 30;
+
+// Parses cache control header and last-modified.
+function parseCacheControl(headers) {
+  var lastMod = headers['last-modified'];
+  var expires = headers.expires;
+
+  var cacheHeaders = {
+    'last-modified': lastMod ? new Date(lastMod) : null,
+    expires: expires ? new Date(expires) : null
+  };
+
+  var cacheControl = headers['cache-control'];
+  if (cacheControl) {
+    cacheControl.split(',').forEach(function(elem) {
+      elem = elem.trim();
+      var i = elem.indexOf('=');
+      if (i === -1) {
+        cacheHeaders[elem] = true;
+      } else {
+        cacheHeaders[elem.substr(0, i)] = elem.substr(i + 1);
+      }
+    });
+  }
+
+  return cacheHeaders;
+}
+
+// Returns the expire time in seconds.
+function maxAge(cacheHeaders) {
+  var expire = cacheHeaders['s-maxage'] || cacheHeaders['max-age'];
+  if (expire) {
+    expire = parseInt(expire);
+  } else if (cacheHeaders.expires) {
+    expire = (cacheHeaders.expires.getTime() - (new Date()).getTime()) / 1000;
+  } else {
+    expire = DEF_EXPIRE;
+  }
+  return Math.min(MAX_EXPIRE, expire);
+}
+
+// Aggregates data and caches it when appropriate.
+exports.handleResponse = function(request, source, dest, options) {
+  var cacheControl = parseCacheControl(source.headers);
+
+  if (!options.cache.use || request.method !== 'GET' ||
+      cacheControl['private'] || cacheControl['no-store']) {
+    // Do nothing for POST and CONNECT requests or when caching is disabled.
+    source.pipe(dest);
+    source.resume();
+    return;
+  }
+
+  // Expire time in seconds.
+  var expire = maxAge(cacheControl);
+  var count = 0;
+  var data = [];
+
+  source.on('data', function(chunk) {
+    count += chunk.length;
+    data.push(chunk);
+    dest.write(chunk);
+  });
+
+  source.on('end', function() {
+    if (expire > 0) {
+      // Cache data.
+      data = Buffer.concat(data);
+      var path = request.headers.path || url.parse(request.url).path;
+      var key = [request.headers.host, path];
+      var header = [source.statusCode, '', source.headers];
+      cache.save(key,
+        { value: [header, data, cacheControl], size: data.length }, expire);
+      request.log('cached %d bytes for %d s', count, expire);
+    }
+
+    dest.end();
+  });
+
+  source.resume();
+};
diff --git a/lib/plugins/index.js b/lib/plugins/index.js
index 0dad597..729c523 100644
--- a/lib/plugins/index.js
+++ b/lib/plugins/index.js
@@ -4,9 +4,10 @@ var Duplex = require('stream').Duplex;
 var PassthroughPlugin = require('./passthrough');
 var GzipPlugin = require('./gzip');
 var DeliverPlugin = require('./deliver');
+var CacheSavePlugin = require('./cachesave');
 
 var plugins = {
-  response: [PassthroughPlugin, GzipPlugin, DeliverPlugin]
+  response: [PassthroughPlugin, GzipPlugin, CacheSavePlugin, DeliverPlugin]
 };
 
 function PipedResponse(response, options) {
diff --git a/lib/proxy.js b/lib/proxy.js
index 4e67251..506e6a6 100644
--- a/lib/proxy.js
+++ b/lib/proxy.js
@@ -4,7 +4,11 @@ var util = require('util');
 var net = require('net');
 var http = require('http');
 var spdy = require('spdy');
+var sync = require('synchronize');
+
 var plugins = require('./plugins');
+var cache = require('./cache');
+var CacheLoadPlugin = require('./plugins/cacheload');
 
 // Shortens the given URL to given maxLen by inserting '...'.
 function shortenUrl(url, maxLen) {
@@ -22,6 +26,7 @@ function shortenUrl(url, maxLen) {
 var SpdyProxy = function(options) {
 
   function handleListen() {
+    cache.init(options);
     console.log('%s listens on port %d', options.name, options.proxy.port);
   }
 
@@ -43,31 +48,38 @@ var SpdyProxy = function(options) {
         shortenUrl(httpOpts.path)
     );
 
-    var forwardRequest = http.request(httpOpts, function(forwardResponse) {
-      forwardResponse.headers['proxy-agent'] = options.title;
+    request.log = function() {
+      console.log('%s\t%s\t%s',
+          new Date().toISOString(),
+          shortenUrl(request.url),
+          util.format.apply(null, Array.prototype.slice.call(arguments, 0)));
+    };
 
-      request.log = function() {
-        console.log('%s\t%s\t%s',
-                    new Date().toISOString(),
-                    shortenUrl(request.url),
-                    util.format.apply(null,
-                      Array.prototype.slice.call(arguments, 0)));
-      };
+    sync.fiber(function() {
+      // Load from cache, if available.
+      var cached = sync.await(CacheLoadPlugin.load(request, response, options,
+                              sync.defer()));
+      if (cached) {
+        return;
+      }
 
-      plugins.handleResponse(request, forwardResponse, response, options);
-    });
+      var forwardRequest = http.request(httpOpts, function(forwardResponse) {
+        forwardResponse.headers['proxy-agent'] = options.title;
+        plugins.handleResponse(request, forwardResponse, response, options);
+      });
 
-    forwardRequest.on('error', function(e) {
-      console.error('Client error: %s', e.message);
-      response.writeHead(502, 'Proxy fetch failed');
-      response.end();
-    });
+      forwardRequest.on('error', function(e) {
+        console.error('Client error: '.error + e.message);
+        response.writeHead(502, 'Proxy fetch failed');
+        response.end();
+      });
 
-    // Pipe POST data.
-    request.pipe(forwardRequest);
+      // Pipe POST data.
+      request.pipe(forwardRequest);
 
-    response.on('close', function() {
-      forwardRequest.abort();
+      response.on('close', function() {
+        forwardRequest.abort();
+      });
     });
   }
 
diff --git a/lib/storage/basic.js b/lib/storage/basic.js
new file mode 100644
index 0000000..cc5f973
--- /dev/null
+++ b/lib/storage/basic.js
@@ -0,0 +1,24 @@
+var basicCache = require('memory-cache');
+
+var TYPE = 'basic';
+
+// Basic in-memory pure JS database.
+var BasicDb = function() {
+  this.type = TYPE;
+};
+BasicDb.prototype.save = function(key, value, expire, onSuccess, onExpire) {
+  basicCache.put(key, value, expire * 1000, onExpire);
+  onSuccess();
+};
+BasicDb.prototype.load = function(key, callback) {
+  var value = basicCache.get(key);
+  callback(null, value);
+};
+
+var instance = new BasicDb();
+
+exports.type = TYPE;
+
+exports.connect = function() {
+  return instance;
+};
diff --git a/lib/storage/index.js b/lib/storage/index.js
new file mode 100644
index 0000000..c940a68
--- /dev/null
+++ b/lib/storage/index.js
@@ -0,0 +1,49 @@
+var basic = require('./basic');
+var redis = require('./redis');
+
+// Available database modules.
+var DATABASES = [basic, redis];
+
+// Creates a new storage connected to given database.
+var Storage = function(db) {
+  this.db = db;
+  this.size = 0;
+  this.memSize = 0;
+  console.log('### new %s storage created', this.db.type);
+};
+Storage.prototype.save = function(key, value, expire) {
+  var that = this;
+  var memSize = value.size;
+
+  function onSuccess() {
+    that.size += 1;
+    that.memSize += memSize;
+    console.log('+++ storage %d items %d MB', that.size,
+        (that.memSize / 1048576).toFixed(2));
+  }
+
+  function onExpire() {
+    that.size -= 1;
+    that.memSize -= memSize;
+    console.log('--- storage %d items %d MB', that.size,
+        (that.memSize / 1048576).toFixed(2));
+  }
+
+  this.db.save(key, value, expire, onSuccess, onExpire);
+};
+Storage.prototype.load = function(key, callback) {
+  this.db.load(key, callback);
+};
+
+// Creates a new storage instance connected to given database type.
+exports.create = function(type) {
+  var db = null;
+
+  DATABASES.forEach(function(d) {
+    if (d.type === type) {
+      db = d.connect();
+    }
+  });
+
+  return db && new Storage(db);
+};
diff --git a/lib/storage/redis.js b/lib/storage/redis.js
new file mode 100644
index 0000000..1d3b536
--- /dev/null
+++ b/lib/storage/redis.js
@@ -0,0 +1,23 @@
+var redis = require('redis');
+
+var TYPE = 'redis';
+
+var RedisDb = function() {
+  this.type = TYPE;
+  this.client = redis.createClient();
+};
+RedisDb.prototype.save = function(key, value, expire, onSuccess) {
+  this.client.set(key.toString(), JSON.stringify(value), onSuccess);
+  this.client.expire(key.toString(), expire);
+};
+RedisDb.prototype.load = function(key, callback) {
+  this.client.get(key.toString(), function(error, reply) {
+    callback(error, JSON.parse(reply));
+  });
+};
+
+exports.type = TYPE;
+
+exports.connect = function() {
+  return new RedisDb();
+};