# Wörterbuch
Wörterbuch is a purely in-memory key/value store that solves a use case somewhere between a database and a message broker.
You can think of it as an alternative to MQTT where you can simply look up messages without having to make a subscription or an alternative to Redis where any SET operation automatically produces a pub/sub message with the key as channel and value as message.
Keys are hierarchical paths in Wörterbuch, similarly to topics in MQTT. The default separator is a `/`, so a key looks something like `some/worterbuch/key`. Values can be retrieved by looking up the key or subscribing to it. In both cases wildcards are supported. The default single level wildcard is `?`, the default multi level wildcard is `#` (all of these can be configured).
Getting `my/key/#` would return a map of all key/value pairs where the key starts with `my/key/`, subscribing to `my/key/#` will produce events for each key/value pair already in store where the key starts with `my/key/` and subsequently an additional event for each SET operation for a key that starts with `my/key/`.