Software Architecture for Modern Web Applications: Complete Guide 2025

Software architecture is what separates a project that lasts 6 months from one that lasts 6 years. After 15 years building web applications in PHP and TypeScript, I can affirm one thing: architectural choices in the first weeks determine 80% of future technical debt.

This guide reviews essential architecture patterns for modern web applications, with concrete examples on the frameworks I use daily.

Why software architecture is crucial in 2025

Web applications are no longer monolithic CRUDs. We handle real-time, microservices, server-hydrated frontends, async queues. Without solid architecture, code becomes spaghetti by the third sprint.

Software architecture answers three fundamental questions:

• Where to put business logic? Not in controllers. Never in controllers.
• How to isolate external dependencies? Databases, third-party APIs, file systems — all must be interchangeable.
• How to test effectively? If testing a business rule requires spinning up a database, architecture has failed.

Major architecture patterns

Hexagonal Architecture (Ports & Adapters)

Hexagonal places the business domain at the center. Interactions with the outside go through ports (interfaces) and adapters (concrete implementations).

[HTTP Adapter] → [Inbound Port] → [Domain] → [Outbound Port] → [DB Adapter]

In Symfony, this translates naturally: PHP interfaces become your ports, Symfony’s autowiring injects adapters. The domain knows nothing of Doctrine, HTTP, or Redis.

The major advantage: you can replace Doctrine with Eloquent (or a JSON file for tests) without touching a line of business logic.

Clean Architecture

Robert Martin’s Clean Architecture organizes code in concentric layers with a strict rule: dependencies always point inward.

• Entities: universal business rules
• Use Cases: application business rules
• Interface Adapters: controllers, presenters, gateways
• Frameworks & Drivers: databases, UI, external services

I’ve applied this approach on several Laravel projects with excellent results. Implementation details are in my article on Clean Architecture with Laravel.

CQRS (Command Query Responsibility Segregation)

CQRS separates read (Queries) and write (Commands) operations into two distinct models. Each side can scale independently, use optimized stores, and evolve without impacting the other.

The pattern makes full sense with a message bus. Symfony Messenger excels in this role — I dedicated a practical guide on CQRS with Symfony to it.

Choosing your architecture by framework

Symfony

Symfony is the framework most naturally aligned with hexagonal architecture. Its service container, event system, and Messenger make it an ideal playground for CQRS and advanced patterns.

For a complex Symfony project, I systematically recommend CQRS + hexagonal. The initial overhead is low thanks to native tooling.

Laravel

Laravel pushes toward MVC and Active Record with Eloquent. It’s efficient for prototyping, but shows limits on large projects. The solution: progressively migrate to Clean Architecture by introducing Actions, DTOs, and Repositories.

The classic trap: putting logic in Eloquent Models or Controllers. Clean Architecture with Laravel shows how to cleanly exit.

Next.js

With App Router and Server Components, Next.js redefines frontend architecture. React Server Components introduce a server/client separation akin to layered architecture.

For full-stack projects, a monorepo with Turborepo lets you structure PHP backend and Next.js frontend in the same repo with clear conventions.

Common mistakes to avoid

1. Over-engineering from day 1. A simple CRUD doesn’t need CQRS. Start simple, refactor when complexity requires it.

2. Confusing layers with folders. Creating a Domain/ folder doesn’t make hexagonal architecture. What matters is dependency direction.

3. Ignoring tests. Good architecture is validated by testability. If you can’t test a use case without a database, review your abstractions.

4. Neglecting documentation. An ADR (Architecture Decision Record) for each structural choice avoids looping debates 6 months later.

5. Copying without understanding. Each pattern solves a specific problem. CQRS without event sourcing, hexagonal without explicit ports — adapt to your context.

In summary

Software architecture isn’t academic luxury. It’s a pragmatic investment that pays off on every subsequent sprint. Hexagonal for isolation, Clean Architecture for layers, CQRS for read/write separation — choose according to your context, team, and domain complexity.

The most important thing remains to set coherent foundations from the start, then evolve them. A project without architecture always ends up paying the price.