Get an introduction to building a CRUD backend that allows users to register and login and then save notes in a MongoDB instance. This crash course uses Kotlin and covers REST APIs from the absolute basics up to building a fully working secured backend. 

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Get the source code for this video here:
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Kotlin Crash Course: https://youtu.be/dzUc9vrsldM?si=8vGs792MWd4_cEyX

00:00 Prerequisites
1:43 - What even is a REST API?
7:25 - What is a backend framework?
9:55 - What we will build
11:02 - Creating a Spring Boot project
15:20 - Project roundtrip
21:18 - Mongo Atlas setup
33:14 - Saving notes to MongoDB
1:06:00 - Base setup for security config
1:12:55 - Checking notes in Mongo Atlas
1:14:24 - Spring's Bean mechanism
1:17:30 - Deleting notes
1:21:05 - Setting up the user collection
1:30:12 - JWT generation & verification
1:57:27 - User registration & login
2:35:55 - Responding with correct status codes
2:44:57 - Field validation
2:52:47 - Trying it out & fixing last bugs

Philipp Lackner

The post is a beginner-friendly crash course for building REST APIs using Spring Boot and Kotlin. It covers the basic knowledge required to follow along, including a brief overview of Kotlin and IntelliJ setup. The course aims to familiarize readers with building a backend application that can handle routes, process data, and interact with MongoDB for storing user-generated notes. Authentication and security are also discussed, with JWT being used as the authentication mechanism.

Full 2025 Backend Dev Crash Course for Beginners With Spring Boot (Kotlin, JWT Auth, MongoDB)