Can I limit concurrent invocations of an AWS Lambda?

I have a Lambda function that’s triggered by a PUT to an S3 bucket.

I want to limit this Lambda function so that it’s only running one instance at a time – I don’t want two instances running concurrently.

I’ve had a look through the Lambda configuration and docs, but I can’t see anything obvious. I can about writing my own locking system, but it would be nice if this was already a solved problem.

How can I limit the number of concurrent invocations of a Lambda?

Solution

AWS Lambda now supports concurrency limits on individual functions: https://aws.amazon.com/about-aws/whats-new/2017/11/set-concurrency-limits-on-individual-aws-lambda-functions/