Function claim_and_lease 

pub(super) async fn claim_and_lease(
    ctx: &BatchFlowContext<'_>,
    conn: &mut PgConnection,
    flow: VerifyFlow,
    limit: usize,
) -> CreditRegistrationResult<Vec<Claimed<VerifyAttempt>>>

Claims up to limit of flow’s due rows, counts an attempt on each and leases it until its next poll would be due, or the iteration’s registry calls run out, so a concurrent iteration cannot poll the same row. Each answer overwrites its own row’s schedule.