DEFAULT_SPIN

The default spin: zero, workers park at once. Spinning is an opt-in optimization for in-memory, high-rate dispatch where messages keep arriving within microseconds of each other: on 4-vCPU CI runners a 20 µs spin made the closed-loop event-dispatch benchmark 0 to 6% faster, 100 µs 16 to 63% faster. With a real store (MongoDB, Redis) the gain was within noise, so it is off by default.