How would you design an Integration Procedure that must process a list of items where each item requires its own service call?

The naive answer is a loop; the good answer considers volume first.

1. Use a Loop Block over the list node, with the per-item action as a child element. This is the correct structure for modest volumes.
2. Ask about volume before committing. A loop that makes one callout per item hits limits and latency quickly. Ten items is fine; a thousand is a different design.
3. For larger volumes, prefer a bulk endpoint if the service offers one — send the whole collection in a single call and map the response back — or move the work to asynchronous Apex invoked by the procedure.
4. Consider chainable execution when the work is genuinely long-running, so partial results can be returned and the user is not left staring at a spinner.
5. Handle partial failure explicitly: decide whether one failed item aborts the batch or is collected into a failure list returned alongside the successes. Silently dropping failures is the trap.
6. Add an execution conditional formula on the inner action so items that do not need the call are skipped rather than sent and discarded.