That's a great question.

Yes, Pony Kafka is currently slower than the C client. But it is also almost completely untuned as of right now. We expect there is a lot of low hanging fruit on that front that will give us significant gains.

There is also the secondary concern regarding the thread pools internal to Pony and librdkafka. We've seen first hand how CPU cache invalidation can impact performance so we are very aware of the potential negatives if the Pony and librdkafka threads ever end up fighting with each other over the same CPU resources.