What do I need to know to create a backend service for an iOS app?

Question

Mobile development

What do I need to know to create a backend service to create an iOS app?

The task of the backend service:

• at the request of the client, send him the url of the images.
  

Additionally:

preferably compatible with MongoDB

Answer 1

I always recommend parse.com for the mobile backend, it is quite suitable for most projects.

Answer 2

At least the language in which you are going to write the backend: php, nodejs, ...

Answer 3

One of the modern backend languages/technologies: python, nodejs, ruby, etc.
The theory of how to develop a REST API.

Answer 4

If you want to work with MongoDB then one of the best options would be Node.js using Loopback or expressjs .