I'm very confused about choosing a micro-framework to build a RESTful API's, all who i asked said that Sinatra (based on Ruby) is the best choice for getting amazing performance, but when i searched a little, I found that Lumen is a nice choice, I developed many applications with Laravel and i felt with its power, i know that Lumen is a Laravel based and for this reason i'm confused.
If you have experience with Laravel already, then I would absolutely build it with Lumen. I have 3 Lumen apps / service in production and they work great and are very performant. I had one instance of a data api needed some higher level functionality and there is a very straight forward upgrade path to Laravel. Add the performance improvements of PHP 7 to the mix and I wouldn't think twice about it.
Lumen is a stripped down version of Laravel. The reason why this is great for APIs is that you don't have the overhead of features that you don't need, e.g. Blade Views, out of the box. You can piece in additional services as needed.
Jonathan Vargas
If your API is pretty simple and doesn't require an ORM, complex routing, and some other things, them Slim is the way to go. Otherwise some more bloated frameworks like Lumen would be okay.