@spyroid what kind of performance? Throughput or latency? How fast do you need? What type of app are you building?
For all the difficulties of using the JNI-wrapped wrapper, I’d always suggest trying out the “regular” JCSMP API first, to see if it has the performance to meet your needs. it might be fast enough? For example, I wrote this simple code to get almost 250,000 msg/s (at 300 byte messages) for Direct messages from a single producer and single consumer: https://community.solace.com/discussion/comment/503#Comment_470
I still have to finish the equivalent Guaranteed producer & consumer test code.
Oh, and re: how to ACK messages? PubSub+ Messaging API Developer Guide