Generic 3-Tier Web Application Architecture

Request

Response

Client

End User

Mobile

PC

User Interface

API Call

JSON Data

Frontend

React

HTML5

CSS3

JS

Vanilla JS

HTTPS / AJAX

Request-Response

(JSON/HTML)

SQL Query

Result Set

Backend API

Application Logic / API

Node.js

Express.js

Java

Spring Boot

Flask / FastAPI

REST / GraphQL API

REQUEST (JSON)

(JSON/HTML)

Business Logic

CRUD Operations /

SQL Queries

Database

MySQL Server

PostgreSQL Server

MongoDB Server

Elastic Search Server

Relational/NoSQL Database

Tables / Schemas / Collection / Documents

SQL