Replace fixed worker shards and Lane locks with one async worker and one FIFO owner per database. Move synchronous SQL, connection work and catalog operations to the blocking pool. Drain accepted work and await final owner receipts before retirement or runtime teardown.
Use a single maintenance task with a short idle grace and at most one pending check per database, so slow owners cannot stall later rounds. Retry transient open failures in the same prepared generation while preserving terminal missing-file checks. Cover lifecycle races, low-FD creation and recovery, and single-worker host shutdown without new shared resource budgets.
ldm0