Rust concurrency and parallelism patterns: threads, message passing with channels, shared state with Mutex and Arc, Send and Sync marker traits, data races vs race conditions, and atomics with memory orderings. Use when writing, reviewing, or refactoring Rust concurrent code: (1) Spawning threads with std::thread and JoinHandle, (2) Using move closures with threads, (3) Message passing with mpsc channels (single and multiple producers), (4) Shared-state concurrency with Mutex and Arc, (5) Understanding or implementing Send and Sync traits, (6) Fixing "cannot be sent between threads safely" errors, (7) Choosing between message passing and shared state, (8) Working with atomics and memory orderings (SeqCst, Acquire, Release, Relaxed), (9) Preventing data races and understanding race conditions, (10) Building thread-safe types with raw pointers.