One of the massive benefits for Rust on Lambda is (as the author mentions) "extremely low start-up time, CPU usage and memory footprint". It's not clear to me if deploying Rust to Lambda via a docker image actually negates some of those benefits.

Using Lambda functions stored in ECR has no impact on performance from my experience. AWS Lambda uses Firecracker under the hood, which builds a VM from a container image. It's likely that non-ECR image based Lambdas are actually packaged as a container image before being launched into a Firecracker VM.

https://aws.amazon.com/blogs/aws/firecracker-lightweight-vir...

Good question! I ran some benchmarks before because I was also curious and besides some slightly larger standard deviation for cold starts execution time, there was so significant difference in performance when using docker.