The AWS JS SDK does a lot. For Lambdas is does too much; it incurs a 1-2 seconds cold-start time, depending on what you load from it. Even for directly loading the smaller clients, it loads 800kb of code from "core". If you really need to squeeze out that extra performance for Lambda cold-starts, you need a smaller client. This client, with dependencies, is less than 10kb (TODO: VERIFY FINAL SIZE). If you are using other thin clients, those dependencies are identical, and share 8kb of the size (its mostly the AWS V4 request signer). This should cost cold-start no more than 100ms, even on the smallest lambda configuration size.
aws-thin-ses does not attempt to offer a complete API replacement, but it is a drop-in replacement for the API it does cover. For ease of use the callback parameter can be ommitted from all async calls to get a Promise instead.