Module leased_ownership 

Clustered single-writer ownership via a Postgres lease row per stream.

One row per active stream — (stream_key, owner_replica_id, epoch, expires_at). try_acquire is INSERT … ON CONFLICT … WHERE expired-or-ours (so it both claims a free stream and reaps an expired one — the shared poll loop is the reaper/takeover, spec §3.3); the owner extends expires_at via heartbeat/renew; renew failing is how a replica learns its lease was stolen. Expiry uses the Postgres clock (now() + make_interval) so it is immune to per-replica clock skew. owns answers from an in-memory mirror of held leases (cheap, for the poll hot path); the UNIQUE(stream_key, seq) store constraint plus the epoch fencing token are the two-writer backstops.

Structs

LeasedOwnership

Clustered Ownership: a Postgres lease per stream (spec §3.3).