AWS NAT Gateway, Fargate, & ECR Cost Gotcha

Andrew Larsen
4 min readNov 19, 2023

At Compoze Labs, we commonly deploy our internal and customer infrastructure to AWS ECS Fargate. We find Fargate to be easy to manage and setup as well as to be able to scale in the long run.

During one of our first large scale implementations we observed a non-obvious networking related issue, involving ECS, ECR, and NAT Gateway that led to an unnecessary spike in cost. I’ll walk through how we discovered the issue and how you can ensure you don’t make the same mistake!

Initial setup and an unexpected bill

To get started, we setup what has now become our standard container architecture in AWS.

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We had our service running and development was well underway. However, we began to noticed that our AWS bill was higher than we were expecting. After digging in further we noticed we had an unusually high amount of data being processed by our AWS managed NAT Gateway. Below is a snippet of our bill after the first week.

We were burning roughly $7 dollars a day just on network traffic alone, and this was just for one service! If we didn’t figure out what was causing this huge spike in traffic, we would be spending hundreds of dollars a month just on network traffic.