Plan an event check-in app that handles repeated scans and walk-ins

Distinguish registration from attendance

PostgreSQL supports uniqueness rules over combinations of fields, such as an event identifier paired with a participant identifier. That can help enforce a chosen attendance rule, but the business must decide the rule first. A registered person has a place in the event's records. A checked-in person has arrived. Do not use one status for both if the organizer needs an accurate attendance count.

Define the identifier staff will use at the entrance, whether it is a code, email search or another appropriate reference. Show enough information to confirm the intended attendee without exposing the full registration list to everyone holding a device. Assign each staff role a clear scope.

• PostgreSQL: constraints ↗

Explain repeated admission attempts

A repeated scan should produce a useful result, such as already checked in with the original time. Decide whether leaving and returning creates a separate entry event or simply displays the existing admission. The interface should help staff make the chosen decision quickly and consistently.

Keep corrections possible. If staff checked in the wrong person, provide an authorized reversal with a reason. Avoid deleting history just to make the counter look right. The organizer may need to understand why a person's admission state changed during the event.

Plan walk-ins and interruptions

If walk-ins are allowed, define the minimum registration information and how capacity is checked. A busy entrance should not have to improvise whether an unregistered guest counts against the same limit. Separate payment collection if it requires a different person or verified external process.

Decide what staff do when connectivity is unavailable. Do not label an app offline-ready without testing the exact behavior, conflict handling and later synchronization. A simple agreed fallback may be more honest than an unverified offline indicator that leads two entrances to admit against different records.

Rehearse the entrance before opening

Use a sample event with registered, cancelled and unknown attendees. Check in one participant twice from different staff devices and inspect the final attendance count. Test searching a common name and correcting the wrong selection, because those ordinary actions can matter more than the ideal scan.

At the end, reconcile attendance with reversals, walk-ins and any fallback records. Keep registration totals separate from actual arrivals in the report. A useful check-in app gives organizers a traceable account of who was admitted while giving entrance staff clear decisions under real operating pressure.