Class KvInbox

Insert-if-absent by id. 'duplicate' means the id is already known (any state); the existing record is returned unchanged. With lease, a new record is created already claimed (processing, token 1, 1 attempt), so no other claimer can take it between the append and the claim.

Lease due records: pending/failed whose nextAttemptAt <= now, plus processing records whose lease expired. Oldest receivedAt first. Each claimed record comes back processing with a fresh fencingToken and attempts + 1.

Lease one specific record when it is claimable (as claim); null when it is not.

processing → done.

processing → failed (due at retryAt, default now) or dead (dead: true).

processing → pending, due now; the claim's attempt is not charged.

Extend the current lease (heartbeat).

Operator replay: any record → pending, due now, attempts reset. No-op for an unknown id.

Records, optionally by state, oldest receivedAt first.

Delete done records completed before doneBefore (and dead ones when includeDead). Returns the count.