diff --git a/platformio/app.py b/platformio/app.py
index b38cc719..6e44e5d0 100644
--- a/platformio/app.py
+++ b/platformio/app.py
@@ -142,31 +142,8 @@ class ContentCache(object):
     def __enter__(self):
         if not self._db_path or not isfile(self._db_path):
             return self
-        found = False
-        newlines = []
-        with open(self._db_path) as fp:
-            for line in fp.readlines():
-                if "=" not in line:
-                    continue
-                line = line.strip()
-                expire, path = line.split("=")
-                if time() < int(expire) and isfile(path):
-                    newlines.append(line)
-                    continue
-                found = True
-                if isfile(path):
-                    try:
-                        remove(path)
-                        if not listdir(dirname(path)):
-                            util.rmtree_(dirname(path))
-                    except OSError:
-                        pass
-
-        if found and self._lock_dbindex():
-            with open(self._db_path, "w") as fp:
-                fp.write("\n".join(newlines) + "\n")
-            self._unlock_dbindex()
 
+        self.delete()
         return self
 
     def __exit__(self, type_, value, traceback):
@@ -190,6 +167,7 @@ class ContentCache(object):
     def _unlock_dbindex(self):
         if self._lockfile:
             self._lockfile.release()
+        return True
 
     def get_cache_path(self, key):
         assert len(key) > 3
@@ -213,20 +191,19 @@ class ContentCache(object):
             return data
 
     def set(self, key, data, valid):
+        cache_path = self.get_cache_path(key)
+        if isfile(cache_path):
+            self.delete(key)
         if not data:
             return
         if not isdir(self.cache_dir):
             os.makedirs(self.cache_dir)
         tdmap = {"s": 1, "m": 60, "h": 3600, "d": 86400}
         assert valid.endswith(tuple(tdmap.keys()))
-        cache_path = self.get_cache_path(key)
         expire_time = int(time() + tdmap[valid[-1]] * int(valid[:-1]))
 
         if not self._lock_dbindex():
             return False
-        with open(self._db_path, "a") as fp:
-            fp.write("%s=%s\n" % (str(expire_time), cache_path))
-        self._unlock_dbindex()
 
         if not isdir(dirname(cache_path)):
             os.makedirs(dirname(cache_path))
@@ -235,6 +212,43 @@ class ContentCache(object):
                 json.dump(data, fp)
             else:
                 fp.write(str(data))
+        with open(self._db_path, "a") as fp:
+            fp.write("%s=%s\n" % (str(expire_time), cache_path))
+
+        return self._unlock_dbindex()
+
+    def delete(self, keys=None):
+        """ Keys=None, delete expired items """
+        if not keys:
+            keys = []
+        if not isinstance(keys, list):
+            keys = [keys]
+        paths_for_delete = [self.get_cache_path(k) for k in keys]
+        found = False
+        newlines = []
+        with open(self._db_path) as fp:
+            for line in fp.readlines():
+                if "=" not in line:
+                    continue
+                line = line.strip()
+                expire, path = line.split("=")
+                if time() < int(expire) and isfile(path) and \
+                        path not in paths_for_delete:
+                    newlines.append(line)
+                    continue
+                found = True
+                if isfile(path):
+                    try:
+                        remove(path)
+                        if not listdir(dirname(path)):
+                            util.rmtree_(dirname(path))
+                    except OSError:
+                        pass
+
+        if found and self._lock_dbindex():
+            with open(self._db_path, "w") as fp:
+                fp.write("\n".join(newlines) + "\n")
+            self._unlock_dbindex()
 
         return True
 
@@ -277,6 +291,12 @@ def set_state_item(name, value):
         data[name] = value
 
 
+def delete_state_item(name):
+    with State(lock=True) as data:
+        if name in data:
+            del data[name]
+
+
 def get_setting(name):
     _env_name = "PLATFORMIO_SETTING_%s" % name.upper()
     if _env_name in environ: