Module wheel 

Hierarchical timing wheel with millisecond resolution.

Six levels of 64 slots cover about 2.2 years; later deadlines wait in an overflow map. Insertion is O(1); each entry moves down at most five times. Removal is lazy: owners check, when an entry fires, that it is still current. Durable timers are rebuilt from journal records on recovery, so the wheel itself is never persisted.

Structs

Wheel