With Flink CEP the first native library for complex event processing in scalable data processing frameworks was introduced. Due to its young history (the first version was released in April 2016) some functional aspects are still open. So a comparison with established CEP software like Esper or Drools is kind of unfair. In future, the Flink CEP library will be extended and first results are already available. Since version 1.1.0 a Scala API for CEP is released which allows developer friendly decsription of event patterns.