diff --git a/src/Content/ContentDb.py b/src/Content/ContentDb.py
new file mode 100644
index 00000000..015c63e6
--- /dev/null
+++ b/src/Content/ContentDb.py
@@ -0,0 +1,116 @@
+import time
+
+from Db import Db
+from Config import config
+
+
+class ContentDb(Db):
+    def __init__(self):
+        self.version = 4
+        super(ContentDb, self).__init__({"db_name": "ContentDb"}, "%s/content.db" % config.data_dir)
+        self.foreign_keys = True
+        self.checkTables()
+        self.site_ids = {}
+
+    def checkTables(self):
+        s = time.time()
+        version = int(self.execute("PRAGMA user_version").fetchone()[0])
+        self.log.debug("Db version: %s, needed: %s" % (version, self.version))
+        if version < self.version:
+            self.createTables()
+        else:
+            self.execute("VACUUM")
+        self.log.debug("Check tables in %.3fs" % (time.time() - s))
+
+    def createTables(self):
+        # Delete all tables
+        self.execute("PRAGMA writable_schema = 1")
+        self.execute("DELETE FROM sqlite_master WHERE type IN ('table', 'index', 'trigger')")
+        self.execute("PRAGMA writable_schema = 0")
+        self.execute("VACUUM")
+        self.execute("PRAGMA INTEGRITY_CHECK")
+        # Create new tables
+        self.execute("""
+            CREATE TABLE site (
+                site_id        INTEGER  PRIMARY KEY ASC AUTOINCREMENT NOT NULL UNIQUE,
+                address        TEXT NOT NULL
+            );
+        """)
+        self.execute("CREATE UNIQUE INDEX site_address ON site (address);")
+
+        self.execute("""
+            CREATE TABLE content (
+                content_id		    INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
+                site_id             INTEGER REFERENCES site (site_id) ON DELETE CASCADE,
+                inner_path          TEXT,
+                size                INTEGER,
+                size_files          INTEGER,
+                size_files_optional INTEGER,
+                modified            INTEGER
+            );
+        """)
+        self.execute("CREATE UNIQUE INDEX content_key ON content (site_id, inner_path);")
+        self.execute("CREATE INDEX content_modified ON content (site_id, modified);")
+
+        self.execute("PRAGMA user_version = %s" % self.version)
+
+    def needSite(self, site_address):
+        if site_address not in self.site_ids:
+            self.execute("INSERT OR IGNORE INTO site ?", {"address": site_address})
+            for row in self.execute("SELECT * FROM site"):
+                self.site_ids[row["address"]] = row["site_id"]
+        return self.site_ids[site_address]
+
+    def deleteSite(self, site_address):
+        site_id = self.site_ids[site_address]
+        self.execute("DELETE FROM site WHERE site_id = :site_id", {"site_id": site_id})
+        del self.site_ids[site_address]
+
+    def setContent(self, site_address, inner_path, content, size=0):
+        self.execute("INSERT OR REPLACE INTO content ?", {
+            "site_id": self.site_ids[site_address],
+            "inner_path": inner_path,
+            "size": size,
+            "size_files": sum([val["size"] for key, val in content.get("files", {}).iteritems()]),
+            "size_files_optional": sum([val["size"] for key, val in content.get("files_optional", {}).iteritems()]),
+            "modified": int(content["modified"])
+        })
+
+    def deleteContent(self, site_address, inner_path):
+        self.execute("DELETE FROM content WHERE ?", {"site_id": self.site_ids[site_address], "inner_path": inner_path})
+
+    def loadDbDict(self, site_address):
+        res = self.execute(
+            "SELECT GROUP_CONCAT(inner_path, '|') AS inner_paths FROM content WHERE ?",
+            {"site_id": self.site_ids[site_address]}
+        )
+        row = res.fetchone()
+        if row and row["inner_paths"]:
+            inner_paths = row["inner_paths"].split("|")
+            return dict.fromkeys(inner_paths, False)
+        else:
+            return {}
+
+    def getTotalSize(self, site_address, ignore=None):
+        params = {"site_id": self.site_ids[site_address]}
+        if ignore:
+            params["not__inner_path"] = ignore
+        res = self.execute("SELECT SUM(size) + SUM(size_files) AS size FROM content WHERE ?", params)
+        return res.fetchone()["size"]
+
+    def getOptionalSize(self, site_address):
+        res = self.execute(
+            "SELECT SUM(size_files_optional) AS size FROM content WHERE ?",
+            {"site_id": self.site_ids[site_address]}
+        )
+        return res.fetchone()["size"]
+
+    def listModified(self, site_address, since):
+        res = self.execute(
+            "SELECT inner_path, modified FROM content WHERE site_id = :site_id AND modified > :since",
+            {"site_id": self.site_ids[site_address], "since": since}
+        )
+        return {row["inner_path"]: row["modified"] for row in res}
+
+
+content_db = ContentDb()
diff --git a/src/Content/ContentDbDict.py b/src/Content/ContentDbDict.py
new file mode 100644
index 00000000..2b1bc8f2
--- /dev/null
+++ b/src/Content/ContentDbDict.py
@@ -0,0 +1,141 @@
+import time
+import os
+
+import ContentDb
+
+
+class ContentDbDict(dict):
+    def __init__(self, site, *args, **kwargs):
+        s = time.time()
+        self.site = site
+        self.site_address = site.address
+        self.cached_keys = []
+        self.log = self.site.log
+        self.db = ContentDb.content_db
+        self.db_id = self.db.needSite(site.address)
+        self.num_loaded = 0
+        super(ContentDbDict, self).__init__(self.db.loadDbDict(site.address))  # Load keys from database
+        self.log.debug("ContentDb init: %.3fs, found files: %s" % (time.time() - s, len(self)))
+
+    def loadItem(self, key):
+        try:
+            self.num_loaded += 1
+            if self.num_loaded % 100 == 0:
+                self.log.debug("Loaded json: %s (latest: %s)" % (self.num_loaded, key))
+            content = self.site.storage.loadJson(key)
+            dict.__setitem__(self, key, content)
+        except IOError:
+            dict.__delitem__(self, key)  # File not exists anymore
+            raise KeyError(key)
+
+        self.addCachedKey(key)
+        self.checkLimit()
+
+        return content
+
+    def getItemSize(self, key):
+        return self.site.storage.getSize(key)
+
+    # Only keep last 50 accessed json in memory
+    def checkLimit(self):
+        if len(self.cached_keys) > 50:
+            key_deleted = self.cached_keys.pop(0)
+            dict.__setitem__(self, key_deleted, False)
+
+    def addCachedKey(self, key):
+        if key not in self.cached_keys and key != "content.json" and len(key) > 40:  # Always keep keys smaller than 40 char
+            self.cached_keys.append(key)
+
+    def __getitem__(self, key):
+        val = dict.get(self, key)
+        if val:  # Already loaded
+            return val
+        elif val is None:  # Unknown key
+            raise KeyError(key)
+        elif val is False:  # Loaded before, but purged from cache
+            return self.loadItem(key)
+
+    def __setitem__(self, key, val):
+        dict.__setitem__(self, key, val)
+        self.addCachedKey(key)
+        self.checkLimit()
+        self.db.setContent(self.site_address, key, val, size=self.getItemSize(key))
+
+    def __delitem__(self, key):
+        dict.__delitem__(self, key)
+        try:
+            self.cached_keys.remove(key)
+        except ValueError:
+            pass
+        self.db.deleteContent(self.site_address, key)
+
+    def iteritems(self):
+        for key, val in dict.iteritems(self):
+            if not val:
+                val = self.loadItem(key)
+            yield key, val
+
+    def items(self):
+        back = []
+        for key, val in dict.iteritems(self):
+            if not val:
+                try:
+                    val = self.loadItem(key)
+                except Exception:
+                    continue
+            back.append((key, val))
+        return back
+
+    def values(self):
+        back = []
+        for key, val in dict.iteritems(self):
+            if not val:
+                try:
+                    val = self.loadItem(key)
+                except Exception:
+                    continue
+            back.append(val)
+        return back
+
+    def get(self, key, default=None):
+        try:
+            return self.__getitem__(key)
+        except KeyError:
+            return default
+
+    def execute(self, query, params={}):
+        params["site_id"] = self.db_id
+        return self.db.execute(query, params)
+
+if __name__ == "__main__":
+    import psutil
+    process = psutil.Process(os.getpid())
+    s_mem = process.memory_info()[0] / float(2 ** 20)
+    root = "data-live/1MaiL5gfBM1cyb4a8e3iiL8L5gXmoAJu27"
+    contents = ContentDbDict("1MaiL5gfBM1cyb4a8e3iiL8L5gXmoAJu27", root)
+    print "Init len", len(contents)
+
+    s = time.time()
+    for dir_name in os.listdir(root + "/data/users/")[0:8000]:
+        contents["data/users/%s/content.json" % dir_name]
+    print "Load: %.3fs" % (time.time() - s)
+
+    s = time.time()
+    found = 0
+    for key, val in contents.iteritems():
+        found += 1
+        assert key
+        assert val
+    print "Found:", found
+    print "Iteritem: %.3fs" % (time.time() - s)
+
+    s = time.time()
+    found = 0
+    for key in contents.keys():
+        found += 1
+        assert key in contents
+    print "In: %.3fs" % (time.time() - s)
+
+    print "Len:", len(contents.values()), len(contents.keys())
+
+    print "Mem: +", process.memory_info()[0] / float(2 ** 20) - s_mem
diff --git a/src/Content/ContentManager.py b/src/Content/ContentManager.py
index a46fe62d..4b4b7aa7 100644
--- a/src/Content/ContentManager.py
+++ b/src/Content/ContentManager.py
@@ -12,6 +12,7 @@ from Config import config
 from util import helper
 from util import Diff
 from Peer import PeerHashfield
+from ContentDbDict import ContentDbDict
 
 
 class ContentManager(object):
@@ -19,10 +20,15 @@ class ContentManager(object):
     def __init__(self, site):
         self.site = site
         self.log = self.site.log
-        self.contents = {}  # Known content.json (without files and includes)
+        self.contents = ContentDbDict(site)
         self.hashfield = PeerHashfield()
+        self.has_optional_files = False
         self.site.onFileDone.append(lambda inner_path: self.addOptionalFile(inner_path))
-        self.loadContent(add_bad_files=False, delete_removed_files=False)
+
+    def loadContents(self):
+        if len(self.contents) == 0:
+            self.log.debug("Content db not initialized, load files from filesystem")
+            self.loadContent(add_bad_files=False, delete_removed_files=False)
         self.site.settings["size"] = self.getTotalSize()
 
     # Load content.json to self.content
diff --git a/src/Site/Site.py b/src/Site/Site.py
index 4a100f6f..0cfc5e0d 100644
--- a/src/Site/Site.py
+++ b/src/Site/Site.py
@@ -52,6 +52,8 @@ class Site(object):
         self.storage = SiteStorage(self, allow_create=allow_create)  # Save and load site files
         self.loadSettings()  # Load settings from sites.json
         self.content_manager = ContentManager(self)  # Load contents
+        self.content_manager = ContentManager(self)
+        self.content_manager.loadContents()  # Load content.json files
         self.connection_server = None
         if "main" in sys.modules and "file_server" in dir(sys.modules["main"]):  # Use global file server by default if possible
             self.connection_server = sys.modules["main"].file_server