Software Architecture Patterns

Monolithic Architecture Single codebase, deployed as one unit.

Structure:
• One application (one process)
• Shared database
• Tight coupling between modules
• Single technology stack

Advantages:
• Simple to develop initially
• Easier testing and deployment
• Single database = data consistency

Disadvantages:
• Hard to scale (must scale entire app)
• Technology lock-in
• Large codebase gets unwieldy
• One bug can crash everything

Suitable for: Startups, small teams, simple applications.

Microservices Multiple small, independent services.

Structure:
• Each service: specific business capability
• Own database per service
• Communicate via APIs (REST, messaging)
• Different tech stacks possible

Advantages:
• Scale individual services
• Teams work independently
• Technology flexibility
• Fault isolation
• Easy to replace/upgrade services

Disadvantages:
• Complex distributed system
• Network latency and failures
• Data consistency challenges
• Operational complexity

Suitable for: Large teams, complex domains, high scale.

Serverless Architecture Function as a Service (FaaS).

Model:
• Write individual functions
• Deployed to cloud (AWS Lambda, Google Cloud Functions)
• Triggered by events (API call, file upload, message)
• Pay per execution
• No server management

Advantages:
• No infrastructure management
• Auto-scaling (handles spikes)
• Pay only for used resources
• Focus on business logic

Disadvantages:
• Cold start latency
• Execution time limits
• Harder to test locally
• Vendor lock-in

Suitable for: Event-driven workloads, variable load, low-maintenance.

Event-Driven Architecture Services communicate via events.

Components:
• Event Producer: publishes events
• Event Broker: distributes events (Kafka, RabbitMQ)
• Event Consumers: subscribe and react

Flow: 1. Something happens (user action, system event) 2. Producer emits event 3. Broker routes to interested consumers 4. Consumers react asynchronously

Advantages:
• Loose coupling (services don't know about each other)
• Highly scalable
• Easy to add new consumers
• Real-time data flows

Disadvantages:
• Complex to understand and debug
• Eventual consistency challenges
• Testing is harder

Suitable for: Real-time systems, complex workflows.

Layered Architecture Organize code into horizontal layers.

Typical 3-tier: 1. Presentation Layer (UI, API) 2. Business Layer (logic, services) 3. Data Layer (database, repositories)

Flow: Request → Presentation → Business → Data → Database

Advantages:
• Clear separation of concerns
• Easy to understand
• Organized codebase
• Testable layers

Disadvantages:
• Tight vertical coupling
• Not ideal for complex domains
• Harder to scale horizontally

Suitable for: Traditional web applications, simple CRUD apps.

API-Driven Architecture Services expose capabilities via APIs.

Characteristics:
• Everything is an API
• HTTP/REST for communication
• Versioned endpoints
• Well-documented contracts
• API gateway as entry point

Benefits:
• Clear service contracts
• Easy integration
• Enables third-party developers
• Decoupling through contracts