How to Set AWS Budget Alerts Properly

What this problem means

AWS Budgets let you set spending thresholds and receive alerts when you cross them. But many teams configure them wrong: SNS not confirmed, Cost Explorer not enabled, or thresholds too high. The result: no alerts when the bill spikes.

Why this is dangerous

- No warning: Without working alerts, you discover problems when the invoice arrives.

- Compounding: Runaway Lambda, scrapers, or forgotten resources can scale costs in days.

- False confidence: "We have alerts" means nothing if they don't fire.

Real-world example

A startup set up a budget at 100% of expected spend. When their bill spiked to $8,000 (from a forgotten RDS instance), they got the alert—but only after they'd already spent the money. Alerts at 50% and 80% would have given them time to act.

How to fix it

1. Enable Cost Explorer: Budgets require Cost Explorer. Enable it in Billing & Cost Management.

2. Create SNS topic: Create a topic, add your email, and confirm the subscription (check spam).

3. Create budget: Use "Cost" type. Set your expected monthly spend.

4. Set thresholds: Add alerts at 50%, 80%, and 100% of forecasted spend.

5. Test: Set a very low threshold (e.g., $1) to verify alerts fire.

Tools and configurations

- AWS Budgets: Billing & Cost Management > Budgets.

- SNS: Create topic, add email subscription, confirm.

- Cost Explorer: Must be enabled.

- IAM: Use AWS-managed policy or ensure `budgets:ViewBudget` and SNS publish.

Common mistakes

- Not confirming the SNS email subscription.

- Only setting 100% threshold—too late.

- Cost Explorer not enabled.

- Wrong budget type (Usage vs Cost).

Quick checklist

- [ ] Enable Cost Explorer

- [ ] Create SNS topic and confirm email subscription

- [ ] Create Cost budget with expected monthly spend

- [ ] Set alerts at 50%, 80%, and 100%

- [ ] Test with a low threshold