A storage is just a class which implements the following interface.
One could use a storage like this:
storage.get(key)(function(value) {
// value is a value or undefined
});
storage.has(key)(function(has_value) {
// has_value is a boolean
});
storage.remove(key)(function() {
// executed as soon as the removal is finished
});
storage.set(key, value)(function() {
// executed as soon as setting the value is finished
});
There are already some storages implemented. There is a MemoryStorage, which is used as default configuration for the session manager. The MongodbStorage, RedisStorage and MysqlStorage is ready, too.