In your example, you compare Lambda against a separate monolith for handling the webhooks, but with a monolith wouldn't the comparison be between lambda and just adding a route and controller (or equivalent) to the monolith?
I'm more thinking of rewriting the application (a bunch of Lambda functions + API gateway + random bits and bobs) as a monolith and running that separately on an EC2 instance (or any other VPS).
In this article, they didn't bolt the serverless architecture onto another existing monolith, but rather rewrote the Step Functions and Lambda functions to be a single ECS task.
In this article, they didn't bolt the serverless architecture onto another existing monolith, but rather rewrote the Step Functions and Lambda functions to be a single ECS task.