Give examples of typical layers in a web application

In a typical web application, the architecture is split into several layers, each playing its own role - from the user interface to the database.

Here is the structure and examples:

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#1. Presentation Layer

Purpose: interaction with the user. What it does: displays data and accepts input. Examples:

• HTML, CSS, JavaScript
• Frameworks: React, Vue, Angular
• Controllers and routers (for example, in Express.js, Django Views, ASP.NET Controllers)
• Forms, buttons, pages, an API interface

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#2. Business Logic Layer

Purpose: implementing the rules and logic of the application. What it does: decides what exactly happens when the user acts. Examples:

• Service classes, managers, handlers (Service, Manager, UseCase)
• Modules that perform calculations, checks, validations
• Frameworks: Spring Services, Django Models/Services, NestJS Services
• Example functions: calculating a price, applying a discount, checking authorization

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#3. Data Access Layer

Purpose: access to the database. What it does: saves, retrieves, and updates data. Examples:

• SQL queries, ORM models (Django ORM, SQLAlchemy, Hibernate)
• Repositories and DAOs (Data Access Objects)
• Connections to PostgreSQL, MySQL, MongoDB, and others

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#4. Infrastructure Layer

Purpose: keeps supporting systems running. What it does: manages external resources, logs, files, networks. Examples:

• Configuration, API clients, queues (RabbitMQ, Kafka)
• Notification services, caching (Redis), logging
• Authentication and authorization (JWT, OAuth)

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#5. (Sometimes) API or Integrations Layer

Purpose: the link between the internal logic and external systems. Examples:

• REST / GraphQL / gRPC controllers
• API adapters for third-party services (payments, email, geolocation)

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Summary: The typical structure of a web application looks like this:

This separation makes the system understandable, modular, and easy to maintain.