Protocol Fallback Timeouts

At the time of item selection, you neither lock them nor check whether they're locked. Tension: someone else could've already grabbed a subset of those. Outcome: the outer update requests a lock and at that point, someone else could've already grabbed a subset of those. | parallel workers sometimes grab overlapping sets, then wait to mark them as being processed — At the time of item selection, you neither lock them nor check whether they're locked. Tension: someone else could've already grabbed a subset of those. Outcome: duplicate their work on the items they happened to share. | I know that it is recommended to use select..for update skip locked — under high data volume and frequent updates/deletions. Tension: it can lead to performance degradation. Outcome: skip locked is the cheapest option.