Language-agnostic guidance for lock-vs-lock-free concurrency decisions, atomic primitives, and memory-ordering risk evaluation. Use when tasks mention atomics, CAS/compare-and-swap, lock-free queues/stacks/pools, memory ordering or memory fences, ABA, weak-memory behavior, or replacing mutexes/locks for performance. Also use when designing custom synchronization primitives or debugging rare concurrency bugs caused by thread interleavings.