Good question. Quite a few... those are very niche products. In fact if I think long on it I am not including the front-end in that 100%. If you want a front-en

Good question. Quite a few... those are very niche products. In fact if I think long on it I am not including the front-end in that 100%. If you want a front-end you'd need a tiny bit of S3 or a server. Lambda is good for stateless APIs and event processing but is not good for anything that requires persistence. SES is an email product so it's usage is niche but it is surprisingly powerful. Example: firing a lambda function when an email bounces or is received. I didn't list a database in there. I'm assuming Trello can be used like a database (and looking at their API it seems it can in this case). So to answer your question: - Any app that requires state - Any app that requires persistent connections - Any app where a unit of work can take more than 6 seconds - Any front-ends [1] - Apps where local cache is needed to provide any sort of reasonable performance - Apps that need a database Cannot be made with just those three tools. [1] It is possible to make a front-end with API gateway and Lambda. API gateway can return different mime types, including HTML. But it would be a huge hack and also not likely cost effective. A static site generated and hosted on S3 with Cloud Front in-front of it is very cost effective but requires the client use javascript. If noscript is a requirement you're stuck with a server.