Expense Tracker API

A secure RESTful backend API for managing personal expenses, built with Node.js, Express.js, and MongoDB. The application provides user registration and authentication using JWT, allowing each user to securely manage their own expenses through complete CRUD operations.

The project demonstrates core backend concepts including REST API design, user authentication, password hashing, authorization, database modeling, and protected resources.

Tech Stack

Technology	Purpose
Node.js	JavaScript runtime for building the backend
Express.js	Web framework for creating API routes and middleware
MongoDB	NoSQL database for storing users and expenses
Mongoose	ODM for defining schemas and interacting with MongoDB
bcrypt	Securely hashes user passwords before storing them
jsonwebtoken (JWT)	Generates and verifies authentication tokens
dotenv	Manages environment variables and sensitive configuration
nodemon	Automatically restarts the server during development

Authentication APIs

Base Route: /api/users

Method	Endpoint	Description	Request Body
POST	/register	Creates a new user account	{ "username", "email", "password" }
POST	/login	Authenticates the user and returns a JWT token	{ "email", "password" }

Expense APIs

Base Route: /api/expenses

Method	Endpoint	Description	Authentication
POST	/	Creates a new expense for the logged-in user	✅ JWT Required
GET	/	Retrieves all expenses belonging to the logged-in user	✅ JWT Required
PUT	/:id	Updates an expense by its ID	✅ JWT Required
DELETE	/:id	Deletes an expense by its ID	✅ JWT Required

Key Features

• User Registration & Login – Users can securely create accounts and authenticate.
• JWT Authentication – Protected endpoints require a valid JWT token.
• Password Security – Passwords are hashed using bcrypt and never stored as plain text.
• Expense CRUD Operations – Users can create, retrieve, update, and delete their expenses.
• User-Level Authorization – Each user can access and modify only their own expense records.
• MongoDB Integration – Mongoose models provide structured interaction with the database.
• Environment-Based Configuration – Sensitive credentials and configuration are managed through .env.

Example Workflow

Register → Login → Receive JWT → Send JWT with Expense Requests → Access Own Expenses

This project is a practical example of how a backend application handles authentication, authorization, RESTful API design, database operations, and secure user-specific data management.