PipelineDB was awesome - built some v. neat things with it 4-5 years ago. Wouldn't use it now since the team went to Confluent. https://ksqldb.io/ functionality is getting close.

Flink is a solid option. Materialize shows a ton of promise.

I also thought of it when I read the question, but looks like after they've been acquired by Confluent the project is essentially dead.