Which AWS Lambda Is Draining Your Budget?

Have you ever wondered how much money you spend running your AWS Lambda functions? Perhaps you considered which function in your microservices ecosystem is more expensive, and which one you can safely ignore because it barely affects your budget. Unfortunately, AWS does not make this easy — its standard console does not provide a straightforward way to see which specific Lambda function costs you hundreds of dollars, and which one only costs a few cents per month.

Why is this information important? Discussions about serverless architectures often focus on performance optimization, scalability, and reliability, but sometimes the key factor of cost is overlooked. Without direct access to detailed cost metrics, you might assume that “Lambda is cheap” or that “everything is fine.” In reality, a single function can cause unexpected expenses for reasons that might not be immediately obvious, such as disk storage. Without this insight, it is difficult to identify what is actually a problem and what is insignificant noise.

This is where my simple open-source tool comes in. It is a script that uses the AWS CLI to retrieve metrics from CloudWatch for all your Lambda functions, calculates their costs, and provides a clear table showing how much you spend on each invocation, how much storage costs, and how much execution time costs. In the GitHub README.md, you will find the script, instructions, and an example report so you know exactly what to expect.

If you want to have a clear understanding of what your AWS Lambda usage costs, and to know where it makes sense to invest time and energy, this script can be a useful resource.