I would recommend Twilio as well. If you're objective is to get off the ground quickly and build something that is robust without much effort, Twilio really nails the developer experience and easy of use. It's also light on any kind of set up or infrastructure as code. That said, it's a lot more expensive that AWS alternatives, so if you're operating at scale you may want to look closer at AWS options.
If you're ONLY using Lambda I would recommend Claudia. It is a lot simpler of a framework and it is also pretty easy to configure and use without having to learn much. If you plan on using the wider AWS ecosystem I would recommend Serverless or SST.
Both Serverless and SST will give you more fine grained control over AWS resources and makes it easier to work with either through CloudFormation or CDK.
For pure RESTful backends you really can't go wrong with any of these. I chose TypeScript with NodeJS because it's what I know and the ecosystem is vast. For most small scale solutions, all of these choices are great. If you have massive needs on the performance side I'd look at Go, and if you have systems level needs then Rust makes sense.