# 06 - REST APIs ## Concepts ### What is a REST API? **Representational state transfer** (**REST**) is a software architectural style that defines a set of constraints to be used for creating Web services. ### What is back-end for an application? ### Why do we need to work with a REST API? To be able to save any user data and progression, we need a back-end system with a storage. ### How to have real time data in your application? ### What are some examples of application that would use realtime websockets vs REST APIs? ### What is a Database? ### Why are there different Databases? ## Project How to sign up for Azure student account? How to set up a web project in Azure? How to create a REST end-point using Azure Functions? How to make a call to your API endpoint? How to test your API endpoint? How to decide on which database you need for your application? How to set-up your first database with Azure? ### How to structure your database? How to change your APIs to save the data to your database? How to retrieve your data from the database? How to reflect your data changes in your application? How to handle errors? ## What could go wrong? What are the security concerns with REST APIs? What kind of bugs are common related to REST APIs? --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://www.xrdev.app/mixed-reality-docs/lessons/lesson-6.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.