The default: one process's memory, at most max live entries. Expired entries are dropped as new ones
arrive, and when every slot holds a live assertion the next one is REFUSED rather than forgetting one
that could still be replayed.
Records id as used until expiresAt, and answers whether it had ALREADY been recorded. Must be
atomic: two concurrent calls with one id must not both answer false.
The default: one process's memory, at most
maxlive entries. Expired entries are dropped as new ones arrive, and when every slot holds a live assertion the next one is REFUSED rather than forgetting one that could still be replayed.