How can I get messages as quickly as possible? I don’t need to acknowledge or anything.

You can use async commit for polling data quickly but there is drawback; you might want to take a look at this thread before applying https://stackoverflow.com/questions/46546174/kafka-consumer-commitsyncvs-commitasync this property. Here's an example of using async commit: https://github.com/Nasdaq/CloudDataService/blob/master/ncdssdkclient/src/main/java/com/nasdaq/ncdsclient/NCDSSession.java#L300