Every free tier has a ceiling, and crossing it does one of two things: the service stops, or billing starts automatically. Launching without knowing which means the incident lands on the day things start working.
Which limits should you check?
- Database storage and concurrent connections
- Monthly request count and bandwidth
- Image and file storage capacity
- Number of emails you may send
- AI API token usage and unit pricing
- Whether the service sleeps after a period of inactivity
How do you prevent a runaway bill?
If you use a paid API, set a daily spending cap and alerts. Most providers offer this and most default it to off. Pair it with rate limiting: once someone loops your endpoint automatically, a cap alone will not recover what already went out.
Incidents do not arrive on launch day. They arrive on the day it starts working. Check your limits before the users show up.