Is using the features of a tool, 'lock in'? You could do the things the tool does yourself but you choose to leverage the tool. That's why you use it. You're aware of this. aws lambda functions can be just pure python or other code. Anything logged there can be a metric in cloudwatch. Users are blissfully aware of how much it's doing for them from security to monitoring. And to be honest companies with enough money would prefer these solutions to something you can knock-up yourself. I feel so locked in by my million free requests a month to service that wont choke that I didn't even have to set-up.