502 Error

I use your system in the state reserve, but more than 300 people enter the reservation at the same time and the system simply collapses and error 502 appears.

I believe there may be many variables and calls in the cart and reservation form. And old codes that don’t work with php 7.3’s performance.

I use nginx and php-fpm.

The page I need help with: [log in to see the link]