This lazy loads the S3 client so it no longer adds ~100 ms to coldstarts if you minify your bundle and don't use S3. If you are using the on disk version of client-s3, it reduces coldstarts by ~300ms. By lazy loading you can also omit client-s3 in a minified bundle if you don't use it reducing the bundled package size by over 340 KB. While making this change I noticed that the call to setConfig when using a custom s3 client was in the run method causing a new S3Client to be created for every request. I moved the setConfig call to the createAPI method so the same S3 client is reused across requests.