Distributed Systems Lessons

How distributed consensus works: the FLP impossibility result, Paxos, Raft leader election and safety, quorums, and the commit rules that keep replicated state machines correct.

Distributed systems fundamentals: the CAP theorem, consistency models, replication, partitioning, and failure modes — reason about any async, multi-service system from first principles.

Idempotency keys done right: dedupe retried requests, store and replay saved results safely, handle concurrent and in-flight duplicates, and reach exactly-once delivery semantics.