# Concurrency — First Principles

## 1. The Principles

### P1. Immutability by Default
Mutable shared state is the enemy. The default is immutable; mutation
is justified.

### P2. Single Responsibility for Threads
Each unit of work has one owner. No "anyone can touch this" state.

### P3. Boundaries are Locks
Synchronization happens at well-defined places. Lock scope is
minimal and explicit.

### P4. Determinism Over Speed
Correct concurrent code is faster than incorrect concurrent code.
Race conditions are not "fast enough" — they are wrong.

### P5. Lock Minimization
Locks are expensive and dangerous. Lock-free, wait-free, and
message-passing are preferred where possible.

### P6. No Silent Races
Race conditions are caught, not hidden. Tools (TSan, Go race
detector) are part of CI.

### P7. Cancellation Support
Every async operation can be cancelled. Cancellation is fast and
complete.

### P8. Timeout Discipline
Every blocking call has a timeout. Forever is not a duration.

### P9. Bounded Queues
Unbounded queues are memory leaks in disguise. Bounded queues
expose backpressure.

### P10. Test for Race Conditions
Concurrent code is tested under concurrent load, not just happy-path
correctness.