How to Set AWS Budget Alerts Properly

Alerts that only fire at 100% are obituaries

AWS Budgets are Cost Optimization evidence only when they page early enough to act. A single threshold at expected spend tells you after the money is gone. Aim for 50% / 80% / 100% of forecasted monthly cost—and prove the pipe works.

One team alerted only at 100%. A forgotten RDS pushed them to multi-thousand spend before the email. Earlier thresholds would have bought time to shut it down.

Make the pipe real

1. Enable Cost Explorer (Budgets depend on it; data can lag ~24h)

2. Create an SNS topic, subscribe your email, confirm (check spam)

3. Create a Cost budget (not Usage) with a realistic monthly number

4. Attach notifications at 50%, 80%, and 100%

5. Test with a temporary $1 threshold until you receive mail

IAM must allow budget view and SNS publish. Wrong budget type or unconfirmed SNS is why "we have alerts" still means silence.

Pair with anomaly detection

Budgets catch plan overrun; Cost Anomaly Detection catches weird shapes. Use both, then fix the underlying runaway (Lambda loops, public APIs, leaked keys)—alerts alone are not a ceiling.