I was excited to see that Pat Helland has published another thought provoking paper: Immutability Changes Everything. If video is more your style, Pat gave a wonderful talk on the same subject at RICON2012 (video, slides).
It's fun to see how Pat's thinking is evolving over time as he's worked at Tandem Computers (TransactionMonitoring Facility), Amazon, Microsoft (Microsoft Transaction Server and SQL Service Broker), and now Salesforce.
You might have enjoyed some of Pat's other visionary papers: Life beyond Distributed Transactions: an Apostate’s Opinion, The end of an architectural era: (it's time for a complete rewrite), and Idempotence Is Not a Medical Condition.
This new paper is a high level overview of why immutability, the idea that destructive updates are not allowed, is a huge architectural win and because of cheaper disk, RAM, and compute, it's now financially feasible to keep all the things. The key insight is that without data updates, coordination in a distributed system becomes a much simpler problem to solve.
Immutability is an architectural concept that's been gaining steam on several fronts. Facebook is using a declarative immutable programming model in both the model and the view. We are seeing the idea of immutable infrastructure rise in DevOps. Aeron is a new messaging system that uses a persistent log to good advantage. The Lambda Architecture makes use of immutability. Datomic is a database data that treats data as a time-ordered series of immutable objects.
If that's of interest, then you'll like the paper.