How does the API connectivity work?

General
1

Hey everyone,
A few months ago I tried integrating a payment system into my Firebase project (a small marketplace app), but I kept running into errors.

I don’t remember every detail, but here’s what I do recall:

The payment API dashboard was receiving some data.

However, my Firebase Functions weren’t working as expected — they failed or threw errors.

So the API connection seemed partially successful, but the backend side never executed properly.

At this point, I’m not sure if the issue was something I misconfigured in Firebase Functions, environment variables, deployment, or authentication with the payment provider.

My questions for the community:

  1. Is integrating external APIs with Firebase Functions normally seamless, or is there some specific setup that people often get wrong?

  2. At what stage are developers typically able to establish a stable API connection — right after deploying Functions? App hosting?

  3. Is there something that commonly breaks when connecting third-party payment APIs (timeouts, CORS, env vars, missing billing activation, etc.)?

Any guidance or tips on what I may have missed would be super helpful. Thanks!

*Its an old project but will retry it again this week

2

  1. Its pretty seamless you can add the APIs to your .env or .env.local or a env.bash your call based on ussage. API_TO_3RD_PARTY=API KEY

    Be sure to rebuild your environment - Easy way to do this is to open your .div.nix file and add a blank row to the end. A button will appear to rebuild the environment in the bottom right of editing that file once you make a change, click it to rebuild the env. Or in your workspace list here Firebase Studio click the three dots and click restart, this will restart the VM entirely, the quicker method is the first method i mentioned as it just rebuilds the environment.

  2. You can use APIs immediately upon setting up your code to call the API and have it correctly established in your environment in the .env file etc.

  3. Nothing commonly breaks except it not being coded in right and the health of the api service you are calling. For instance, if i wanted to call an API for weather, one day it might work great, but another it might not work at all due to the API being down or slow because of volume etc. The dev environment or final product is simply creating a connection to that API and if everything is coded correctly then it will be a problem with the API provider typically.

I hope this helps as i am not the most qualified to answer but i know enough!

God speed