A background job reads clock_timestamp() from Postgres as a cutoff, then passes it back as a parameter (`where queued_at < ${cutoff}::timestamptz`). With a custom postgres.js type for timestamptz (serialize: x => new Date(x).toISOString()), the parameter is serialized through a JS Date, i.e. to the millisecond. Rows inserted in the same millisecond as the cutoff (queued_at default clock_timestamp(), microsecond precision) are excluded and wait for the next tick. Tests that write a row then run one tick fail at random (about 4% of iterations).