When I first started practicing AWS through labs, I used to log into AWS Cost Explorer every morning to make sure I am not spending too much money. Even though, I set up CloudWatch and Budgets, I wanted to make sure it was right all the time.
Then one day, my costs had doubled overnight. No new projects, no big changes or so I thought.
Turned out a test EC2 instance that was “temporary” never got shut down, and on top of that, there was a data transfer spike I hadn’t noticed. Both small oversights, but together they led to a painful surprise on the bill.
If you’ve ever had that sinking feeling when your AWS costs look way higher than expected, you’re not alone. For that reason, I put in place a systematic way to track down the culprit.
Here are 5 tips I follow when costs look off:
1. Review Cost Breakdown by Service
- Go to Cost Explorer → Service Breakdown.
- See which service is driving the spike. EC2? S3? Data Transfer? That’s your first clue.
This gives you a clear picture of which AWS service is driving the increase.
2. Check for Unexpected Resources
- Open AWS Config → Resource Changes.
- Look for new instances, databases, or buckets you didn’t plan for. Sometimes a test resource gets left running.
A forgotten test environment running all weekend can be an expensive surprise.
3. Identify Data Transfer Spikes
- In CloudWatch → Metrics → Network Usage, check for sudden jumps in outbound traffic.
- High data transfer can add up fast, especially across regions or internet-facing traffic, can rack up costs quickly. If you see a sudden spike here, you’ve likely found part of the problem.
See tip 4 and 5 below.
4. Set Up Budgets and Alerts
- Go to AWS Budgets → Create Budget and set up alerts.
- This doesn’t solve the current issue, but it prevents future headaches by warning you when spending crosses your threshold.
5. Review Trusted Advisor for Cost Optimization
- Finally, check AWS Trusted Advisor → Cost Optimization.
- It will flag idle or underutilized resources you can shut down or resize, helping you trim costs moving forward.
Unexpected costs in AWS are often the result of small oversights piling up. With this checklist, you can spot problems faster, take corrective action, and set up guardrails to prevent a repeat.
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