Message-passing is a necessary but insufficient abstraction. It's not pixie dust, but if you want to build a robust and organized system you'll probably want to reach for it. For the data integrity issue, you need to have a strong data model implemented upon your message-passing architecture, like an immutable event log. Project useful aggregations and indices from that. I'm wrapping up an implementation of exactly this today (Node.js + Kafka = poor man's Erlang actors), AMA. Email is in my profile as well.