When multiple people already have a Google Form open, a response limit is not the same thing as a transactional reservation system. The form may still receive a small overshoot around the last available seat.
A form can only close after a submission is processed. If several people opened the form before the limit was reached, they may all still attempt to submit.
A visitor who opened the form earlier may still be looking at a valid page even after capacity is almost gone.
If multiple people submit at roughly the same time, one rule update may arrive a little later than the final visible seat.
Apps Script reacts quickly for normal operations, but it is not a hard real-time locking system.
For low-volume forms this is usually fine. For high-demand launches, it needs a clearer plan.
Google Forms can stop accepting responses manually, collect timestamps, and show a closed-form message once the form is closed.
It does not provide seat locking, queueing, or atomic reservation logic for people who are already in the form.
Apps Script can watch submissions, close the form after a cap, and notify the owner without manual monitoring.
A script can reduce oversubscription risk, but it still cannot turn Google Forms into a strict booking engine.
FormGuard is strongest when the form needs clear operational controls, not transactional guarantees.
Classes, workshops, volunteer signups, intake windows, office hours, and internal request forms with moderate traffic.
Public launches, scarce seats, or situations where even one extra confirmed spot creates a real operational problem.
Combine a response cap with scheduled open and close times, custom close messaging, and owner notifications.
Do not position FormGuard as a zero-race-condition booking engine or a guaranteed hard inventory lock.