KSQL allows users to build their own custom functions for processing data in Kafka. Most of the examples that can be found online are helpful, but are often simplistic. This discussion will dive deeper than most tutorials on the subject by showing examples of more advanced UD(A)Fs, and will inspire listeners to venture beyond the hello world tutorials into more exciting territory. First, we will learn how to remove most of the boilerplate that is involved when building even simple KSQL functions. Then, building on this foundation, we will build UDFs that leverage both cloud-based Machine Learning / AI services and also embedded predictive models. Finally, we will venture into more experimental territory and leverage GraalVM + polyglot programming to build multilingual UDFs (UDFs that are written in languages other than Java).