My repl serves (flask) the relevant pages after pressing the run button. However it stops after an hour. I don’t know how to keep it alive or make it restart when someone makes a request. Here is my REPL: https://replit.com/@KarthikArcot/cpplox
What do you mean by “stops”, even the paid keep-alive feature sleeps sometimes, but with a pinger it usually has a fast response. Note, that when it wakes up, it calls the run command, and you have a very odd run command. You might want to fix that. It compiles before starting, so when it wakes up it Re-compiles, slowing the wake-up time.
The best solution to this would be to purchase Always-On for that repl and use a web pinger at the same time. If your repl crashes due to an error, it won’t boot up again to prevent crashlooping.