My LambdaCents Project Story

What Inspired Me

In modern cloud environments, teams rapidly spin up resources without always knowing the cost impact upfront. During a hackathon focused on AWS Lambda, I wanted to build something practical that not only used Lambda but also solved a real-world problem: helping teams estimate cloud costs in real time based on tagging. The idea of combining event-driven architecture with cost visibility felt like a perfect way to learn and contribute to FinOps.

What I Learned

This project deepened my understanding of AWS CloudTrail, EventBridge, and the AWS Pricing API — services I had only lightly touched before. I also got hands-on experience with Lambda triggers beyond the usual API Gateway, exploring how to respond to infrastructure events. Writing cost estimation logic taught me about the complexity of AWS pricing and the importance of assumptions in automation.

How I Built It

1. Enabled CloudTrail to log API activity.
2. Created an EventBridge rule to listen for resource creation events, filtering specifically for tagged resources.
3. Developed a Python Lambda function to:
   • Parse the incoming event,
   • Retrieve resource tags via boto3,
   • Query the Pricing API or apply cost logic to estimate monthly cost,
   • Log or notify about the cost estimate.
4. Managed infrastructure using Terraform to keep deployments repeatable and auditable.

Challenges Faced

• Understanding how to filter CloudTrail events correctly in EventBridge was tricky initially, especially narrowing down to relevant resource creations.
• The AWS Pricing API is complex and sometimes inconsistent, which required fallback logic and assumptions for reliable estimates.
• Ensuring Lambda had the right IAM permissions to access tags and pricing data took careful trial and error.

Overall, this project pushed me beyond my comfort zone and gave me valuable insight into event-driven AWS cost management.

Built With

• amazon-web-services
• lambda
• python
• terraform