Preventing Abuse: Cloud Functions for Firebase

Question

What is the best way to stop an attacker from triggering a Cloud Function repeatedly, causing a huge bill or causing the project to run into quota limits?

Some ideas:

Answer 1

Check my answer here.

Short breakdown of items from my answer :

1. Limit the type of requests
2. Authenticate if you can
3. Check for origin
4. Use a load balancer in between
5. Use something like Cloudflare Page Rules

Hope it helps :)