We are seeing event sourced systems used in more and more places, but many people are finding it difficult to do effectively. We’ve used Kafka in many instances, and have found it to be a great match for event sourcing. This article does a greate job of explaining how.
At Massive Difference, we’ve built event sourced financial systems, and can tell you there are a lot of non-obvious facets to building one. We think this post over at Chris Kiehl’s blog does a fantastic job of pointing out some of the sharp edges you will run into that you might not have anticipated.