Function update 

pub fn update(
    states: &mut HashMap<String, CredentialState>,
    generations: &mut HashMap<String, u64>,
    next_generation: &mut u64,
    cmd: Command,
) -> Vec<Event>

states is the orchestrator’s whole coordination table; generations tracks each id’s CURRENT registration epoch so a completion from a superseded registration can be told apart from a current one (see Event::RunFreshnessCheck’s doc comment); next_generation is a single counter shared across ALL ids, strictly increasing, never reused — deliberately NOT a per-id counter restarted at 0 on each Register, because an unregister-then-re-register sequence would then hand the new registration the SAME generation number the old one had, and a stale completion from the old registration (still in flight when the unregister/re-register raced in) would wrongly pass the staleness check instead of being discarded (reagent re-review on #2275). One reducer call per dispatched command, sub-millisecond, never awaits.