Stateful Service Design Questions

Design services that maintain state across requests and nodes and reason about their correctness and reliability. Topics include consistency models and trade offs, transactions and isolation, replication and leader election, sharding and partitioning strategies, cache design and eviction policies, durable queues and ordering guarantees, idempotency and concurrency control, failure modes and recovery patterns, and operational concerns such as backups, migrations, and testing for stateful components.