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Limit amount of subscriptions

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Dear Caspio community,


I have an in depth question regarding the following tutorial: Limit the number of submissions

To get a better understanding of my issue I make use of the next example.


I want to make an app for booking seats at a movie. Just like in the tutorial i use 3 datapages for this.

  1. Search form - for searching movies.

  2. Booking form - for booking movies.

  3. Auto-update form - for increasing the number of booked_seats.


When a customer searches a movie he will have to go to the details page. The datapage determines if there are any seats available by checking if: booked_seats < max_available_seats. When this is the case a link is presented to the booking form where the  customer can book a seat for the movie, after submitting the booking form the booked_seats variable is increased by 1.


But, the following issues arise:

  1. The booked_seats variable is only increased after submitting the booking form. When there is only one seat left it is therefore possible that two customers get redirected. This would result in a double booking. (booked_seats = 11, max_available_seats = 10).

  2. When the admin of the movie wants to delete a record (a booking) the number of booked_seats remains the same.


So, my questions are:


  1. How to prevent double bookings? My idea was when the first customer presses the link his seat is reserved for 5 minutes, like some sort of “session”.

  2. How to decrease the number of booked_seats when a record is deleted? Or, even better, how to retrieve a realtime amount of bookings from my bookings_table?

I hope someone can help me with this matter. If you need any additional information regarding this issue, feel free to ask.


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The provided solution is not recommended. Look at Drawback.

In this implementation there is no validation if users access the submission form directly.

Since it is a browser side programming there ways to hack it. It is better if  you have developers custom program it and have a trigger to change the number. This way delete and double booking issue will no longer exist either.

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