There are a finite set of this to trigger the function and they become central to API Gateway, kinsesis, s3 change/addition... It definitely has more lock in

There are a finite set of this to trigger the function and they become central to API Gateway, kinsesis, s3 change/addition... It definitely has more lock in potential than more "vanilla" offerings like EC2, RDS, S3. You could name a replacement/competitor service for each of the above, but if the Lambda is triggered by S3 changes then that's a big barrier to putting your static files elsewhere