Lambdas, at least the JS ones, are Node.js based and not hard at all to migrate to an alternative cloud service. You can even use a framework that handles all the cloud-specific functionality for you and works across AWS, Azure, GCloud, etc: https://www.serverless.com/
The lock-in really comes from AWS-specific services. Redis, Mongo, etc will have the same API no matter where you're hosting them, so it's pretty trivial to point your client-side code to a different cloud-hosted Redis instance if you find AWS lacking there.
The lock-in really comes from AWS-specific services. Redis, Mongo, etc will have the same API no matter where you're hosting them, so it's pretty trivial to point your client-side code to a different cloud-hosted Redis instance if you find AWS lacking there.