Ask HN: Back end engineer trying to build a mobile app, would love some guidance

I've recommended a "web app first" approach to some of my clients.

You might find parse.com services cover your user and notifications requirements, and perhaps even your REST backend.

To get to a mvp and prove that you're concept work, you don't have to (and maybe shouldn't) build a native app for every platform. The goal of the mvp is to get the product in front of people as fast as possible, to see if they would spend a few minutes using your products, or if it's not useful for them. Once you validate this, you can think of expanding to other platforms.

I would suggest to only go for the platform where you're most comfortable developing with. Web app can be good indeed, but if you already know objective c or java then you'll be probably better off going for native iOS or Android first. Good luck!

The first thing I would do is think about what capabilities you need in order to successfully execute the product, and equally important how you would want to distribute the product. Depending on the answers, I would then find a framework (or multiple frameworks) that facilitate the approach you want to take. This will allow you to prototype faster (and reiterate faster as you learn from your customers). This would also play in to how you approach building the back end.

From reading your replies to other comments, it sounds like you want access to a phone's local resources, and you are possibly interested in using web technologies. I would look into Apache Cordova (aka PhoneGap) or something similar (there are many). This allows you to build once with HTML/CSS/JS, and then distribute via Android/iOS and more (differentiation being each platform would need specific front end JS code to access the phone's local resources). This approach is commonly used in conjunction with a back end that accepts API Requests (aka front end makes Ajax request, back end responds with Data). I'm using this approach for one of my current projects.