Architecture
Backend refers to the server-side layer of an application that handles business logic, data processing, authentication, and communication with databases and third-party services — invisible to the end user but powering everything they experience.
Backend systems receive requests from frontend clients or other services, execute business rules, query or write to databases, and return structured responses, typically as JSON over HTTP. Common backend technologies include Node.js, Python (Django/FastAPI), Java (Spring Boot), Ruby on Rails, and Go, each with different strengths in performance, developer velocity, and ecosystem maturity. Backend architecture choices — monolithic, microservices, serverless — determine how the system scales, how teams are organised, and how difficult it is to deploy changes independently. Security is a primary backend concern: authentication, authorisation, input validation, rate limiting, and data encryption must all be implemented at this layer to protect application and user data.
Example
When a user submits an expense report in a finance app, the backend validates the amounts, checks approval rules, writes records to PostgreSQL, triggers an email notification, and returns a confirmation response to the frontend.
Related terms
Frontend
Frontend refers to the client-side layer of a web or mobile application — everything the user sees and interacts with directly, including layout, visual design, navigation, and interactive behaviour rendered in the browser or on the device.
Full-Stack Development
Full-stack development refers to the practice of building both the frontend (client-side) and backend (server-side) components of a web application, giving a developer end-to-end ownership of the entire technology stack.
Database
A database is an organised collection of structured or semi-structured data stored electronically and managed by a database management system (DBMS) that enables efficient querying, insertion, update, and deletion of records.
API (Application Programming Interface)
An API is a defined set of rules and protocols that allows one software application to request and exchange data or functionality with another, acting as a structured contract between systems.
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