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Design Patterns

This document summarizes key software design patterns, architectural principles, and related concepts for building robust applications.

Creational Patterns​

Inversion of Control & Dependency Injection​

Inversion of Control (IoC) is a design principle where the control flow of a program is inverted, and Dependency Injection (DI) is a technique to implement IoC by passing dependencies to objects rather than creating them internally.

💡 This promotes loose coupling and testability.

📝 Martin Fowler - Inversion of Control Containers and the Dependency Injection pattern (2004)

Architectural Patterns​

Hexagonal Architecture​

Also known as Ports and Adapters, this architecture isolates business logic from external systems (e.g., UI, databases) through well-defined interfaces (ports) and implementations (adapters). It enhances modularity and testability.

💡 Ideal for microservices and systems requiring flexibility in swapping out external dependencies.

📝 Read more:

Data Access Patterns​

Active Record​

An object that wraps a row in a database table, encapsulating both data and behavior (e.g., CRUD operations). Common in ORMs like Ruby on Rails.

💡 Simple for small applications but may couple business logic too tightly to the database.

📝 Martin Fowler - Active Record (2003)

Table Data Gateway​

An object that acts as a gateway to a database table, providing a simple interface for all SQL operations on that table.

💡 Useful for encapsulating database access logic, especially in systems with complex queries.

📝 Martin Fowler - Table Data Gateway (2003)

Row Data Gateway​

An object that represents a single row in a database table, acting as a data holder without business logic.

💡 Works well with Table Data Gateway for separating data access and manipulation.

📝 Martin Fowler - Row Data Gateway

Feature Flags​

Feature flags enable continuous deployment by allowing new functionality to be deployed but toggled on/off without redeployment. They support progressive exposure but come with management overhead.

💡 Useful for A/B testing, canary releases, and managing feature rollouts in production.

Willy-Peter Schaub - What's the cost of feature flags? (2018)

Communication Protocols​

REST​

Representational State Transfer (REST) is a widely-used architectural style for designing networked applications, relying on stateless, client-server communication via HTTP.

💡 As of 2025, REST remains the dominant choice for APIs due to its simplicity and compatibility.

gRPC​

A high-performance, open-source framework for remote procedure calls, using HTTP/2 and Protocol Buffers. It’s optimized for microservices and low-latency communication.

💡 gRPC is gaining traction for new microservices due to its performance benefits over REST.

📝 Read more:

Authentication​

Mechanisms to verify user or system identity, often involving tokens for secure access.

Refresh Tokens​

Tokens used to obtain new access tokens without re-authenticating, improving security and user experience.

💡 Essential for secure API access, especially in distributed systems.

📝 Auth0 - Understanding Refresh Tokens

Additional Resources​