DRY and Code Reuse Principles

Tool-agnostic, language-agnostic development principles for understanding DRY, code reuse, and abstraction strategies.

I need to...

I need to...	Guide	Summary
Understand what DRY actually means	DRY Overview	When making architectural decisions about code organization, abstraction, and knowledge representation across your entire software system.
Know when duplication is acceptable	Four Types of Duplication	When analyzing whether duplication in your codebase is problematic and deciding how to address it.
Choose between DRY, WET, or AHA approaches	DRY vs WET vs AHA	When deciding whether to abstract duplicated code or let it remain duplicated, especially early in a feature's lifecycle.
Identify code duplication in my project	Code Duplication	When identifying and deciding how to address duplicated code blocks in your codebase.
Ensure single source of truth for business rules	Knowledge Duplication	When ensuring business rules, validation logic, data schemas, and domain knowledge exist in only one authoritative place.
Learn abstraction strategies	Abstraction Strategies	When deciding how to eliminate duplication through abstraction — choosing the right abstraction mechanism for the situation.
Know when it's safe to abstract	Rule of Three	When deciding whether it's time to refactor duplicated code into an abstraction.
Apply DRY to configuration	DRY in Configuration	When managing application configuration, environment variables, feature flags, and settings across environments.
Apply DRY to documentation	DRY in Documentation	When writing and maintaining technical documentation, API docs, code comments, and system documentation.
Apply DRY to tests	DRY in Testing	When writing test suites and encountering repeated setup, teardown, or assertion patterns across tests.
Apply DRY across system boundaries	DRY Across Boundaries	When dealing with knowledge duplication across system boundaries: microservices, frontend/backend, multiple programming languages, or separate repositories.
Avoid over-abstraction	Over-DRY Anti-Patterns	When evaluating whether an abstraction is helping or hurting, and when to choose duplication over the wrong abstraction.
Get a practical decision framework	Best Practices Decision Framework	When making architectural decisions about abstraction, duplication, and code organization.
Detect duplication in my codebase	Code Smells and Detection	When reviewing code, performing maintenance, or evaluating technical debt related to duplication.
Find authoritative sources	Code Reference Map