Hi @amit,
Oh, no! It looks like somewhere, something is parsing that JSON response as a floating-point number – and large floating-point numbers cannot record large integers accurately!
There are a lot of possibilities for what might be causing this issue: If you’re on the client, then the bad news is that this is probably happening in the browser, which works in Javascript where all numbers are floating-point, so there’s not a lot you can do to stop it. My recoommendation would be to update your service to send the user ID as a string, instead of a number.
If you’re on the server, it’s possible that something in anvil.http.request() is doing unnecessary floating-point parsing – you could try using requests instead and seeing if it handles it better.