Correctness — Software Architecture

Consistency Model Selection comparison

When to use linearizability vs causal vs eventual consistency; timeliness vs integrity distinction; decision guide by scenario (locks, balances, feeds, shopping carts, multi-region); read routing as the practical knob; CAP trap warning

Consistency Models concept

Full spectrum: linearizability, sequential, causal, strong eventual, eventual; COPS causal+ implementation; isolation levels; linearizability ≠ serializability; timeliness vs integrity; safety vs liveness

CRDTs (Conflict-free Replicated Data Types) concept

Conflict-free Replicated Data Types; semilattice + LUB merge; strong eventual consistency; LWW/MV registers; CALM theorem (application-level consistency, not linearizability)

Idempotency concept

Idempotency keys (atomicity requirement, principle of least astonishment), at-least-once delivery, retry safety

System Models concept

Link models (fair-loss/reliable/authenticated), process failure models (Byzantine/crash-recovery/crash-stop), timing models (sync/async/partial sync); default assumptions