2. Learn Flutter Backend Basics #

Before connecting Flutter apps to real servers, every developer must understand the fundamentals of backend development. These concepts form the foundation for building APIs, managing databases, implementing authentication, and ensuring application security.

Backend development involves handling data processing, business logic, authentication, and communication between the client and server. Even if you use ready-made solutions like Firebase or Supabase, understanding backend basics is essential.

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Core Backend Topics #

1. How Backend Works #

A backend is the “behind-the-scenes” part of any application. It handles:

• Data storage (database)
• Authentication (login, signup)
• Business logic (rules, calculations)
• API responses
• File handling (images, documents)
• Security and permissions

Backend Workflow #

1. Flutter (client) sends a request
2. Backend receives the request
3. Server processes the request
4. Server interacts with the database
5. Server returns a JSON response
6. Flutter displays data to the user

The backend essentially acts as the brain of your application.

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2. Databases: SQL vs NoSQL #

SQL Databases (Structured Data) #

• Use tables, rows, and columns
• Follow predefined schema
• Support complex queries

Examples:

• MySQL
• PostgreSQL
• SQLite
• SQL Server

Use SQL when:

• Data is structured
• You need strong relationships (foreign keys)
• You want ACID transactions

NoSQL Databases (Unstructured / Semi-structured Data) #

• Flexible schema
• Store data in JSON-like format
• Highly scalable

Examples:

• MongoDB
• Firebase Firestore
• DynamoDB
• CouchDB

Use NoSQL when:

• Data is flexible or nested
• You need fast scalability
• Real-time applications

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3. Authentication and Authorization #

Authentication #

Verifying who the user is.
Example: Login with email & password.

Authorization #

Checking what the user is allowed to do.
Example: Admin can update products, but a normal user cannot.

Common Authentication Strategies:

• Email/password
• OAuth (Google, Facebook, GitHub)
• JWT tokens
• API keys

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4. Sessions, Tokens, Cookies #

These help in maintaining user login state.

Sessions #

• Stored on the server
• Client receives a session ID

Good for traditional web apps.

Cookies #

• Small storage on the client
• Stores session ID or small data

Used mainly in browser-based apps.

Tokens (e.g., JWT) #

• JSON Web Tokens
• Self-contained (user info + expiry)
• Sent with every request
• Works perfectly with Flutter (mobile apps)

Example JWT structure (decoded):

{
  "id": 1,
  "email": "ali@example.com",
  "exp": 1709980800
}

Tokens are the most popular method for mobile app authentication.

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5. API Security Basics #

Security is essential for protecting your backend and user data.

Key Security Practices:

• Use HTTPS only
• Validate all incoming data
• Use JWT tokens for API authentication
• Rate limiting to prevent abuse
• Avoid exposing sensitive data
• Use hashed passwords (bcrypt, Argon2)
• Define proper user roles (admin, user)

Server-side validation is always required, even if you validate in Flutter.

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6. CRUD Operations #

CRUD means:

Operation	Meaning	HTTP Method
Create	Add new data	POST
Read	Fetch data	GET
Update	Modify existing data	PUT/PATCH
Delete	Remove data	DELETE

Example API Endpoints for CRUD:

POST   /users
GET    /users
GET    /users/10
PUT    /users/10
DELETE /users/10

This is the foundation of REST API development.

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7. MVC Architecture #

MVC stands for Model–View–Controller, a common pattern in backend frameworks like Express.js, Laravel, Django, NestJS.

Model #

Handles database structure and logic.
Example: User model.

View #

Not used in API-only backends (Flutter handles UI).

Controller #

Receives requests and returns responses.
Example: UserController handles login, signup, update user.

Folder Structure Example:

/models
/controllers
/routes
/config

MVC helps keep the code organized and scalable.

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8. Environment Variables #

Environment variables store sensitive or configurable values that should not be hardcoded.

Examples:

• Database URL
• API keys
• Secret keys for JWT
• Cloud storage credentials

Example .env file: #

DB_URL=postgres://username:password@localhost:5432/mydb
JWT_SECRET=my-secret-key
PORT=5000

These variables are accessed in backend code and hidden from public.

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Best Practices for Backend Learning #

✔ Understand how APIs work before choosing a tech stack
✔ Learn SQL basics (joins, queries, tables)
✔ Learn NoSQL when working with flexible data
✔ Always secure your API
✔ Use MVC or modular architecture
✔ Never store passwords as plain text
✔ Use environment variables for hidden configurations
✔ Practice building CRUD APIs
✔ Test APIs using Postman or Thunder Client