[onion2k]

It's trivial if your app is just CRUD with domain specific fields, but there can still be some tricky parts;

* Sync'ing data between the frontend and backend if your app has any sort of offline capabilities. Conflict resolution is hard if you want anything better than just a dumb overwrite of what's there.

* Data munging for anything that isn't coming from a well defined API is a horrible and difficult task.

* Scaling and replication on a global scale is still a challenge. It doesn't affect many apps though.

You can knock up a decent REST API in Laravel/Express/Django/whatever in a few hours, but getting the data that you push through it still represents some fun and challenging aspects of app development.

[findjashua]

Agree, those are all challenging problems to solve, but I haven't had the chance to work on them

1. we don't support offline mode in our app. Though, quite a few databases have a version number in their documents (es, couch etc), so the user can be shown conflicts if the server responds with a version mismatch

2. Luckily, I haven't had to work with any overly terrible APIs. The documentation is usually bad, but fiddling around with the req params/body usually gets me what I want

3. We're selling to businesses, so our traffic isn't at that scale.