1. Why API Design Patterns Matter

API design patterns are repeatable, reusable approaches to structuring API operations based on the nature of the underlying business capability or workflow.

These patterns define how an API exposes functionality — whether as simple resource manipulation (CRUD), state-changing actions (commands), lifecycle transitions (extended CRUD), read-optimized queries, long-running jobs, events, or composite responses.

Patterns help teams avoid “inventing a shape” for every endpoint and instead choose from proven approaches tailored to specific problem types.

1.1. The Value of Patterns

Consistency across teams and APIs. Using consistent patterns ensures that developers and API consumers know what to expect. When APIs feel familiar, onboarding is faster, and the learning curve shrinks — especially for platforms with dozens or hundreds of services.

Improved consumer experience. Patterns shape how easy or difficult it is for consumers to understand “how to do something” with your API. A clear, intention-revealing pattern provides faster time to first success, fewer integration errors, and fewer support escalations.

Governance and quality improvement. Patterns act as “preapproved design templates.” This reduces ambiguity, accelerates design reviews, and ensures compliance with platform standards (naming, versioning, error handling, pagination, security). By aligning to patterns, teams naturally avoid common API anti-patterns that otherwise require governance intervention.

Higher maintainability over time. When internal APIs follow consistent interaction styles, teams spend less time interpreting bespoke conventions and more time delivering new capabilities. Refactoring, versioning, and lifecycle management become easier because the underlying pattern is predictable.

1.2. Patterns vs. Architectural Styles

Patterns are interaction shapes; styles are broader architectural approaches.

Many teams mistakenly equate CRUD with REST or commands with RPC. In reality:

  • REST describes constraints like statelessness, uniform interface, HATEOAS — not CRUD.
  • RPC describes a communication style — not how you design domain actions.
  • Patterns describe how individual operations behave regardless of the underlying architecture.

Position patterns as “interaction-level design choices” that sit beneath architectural style but above low-level implementation details.

1.3. How to Choose a Pattern

Capability-first thinking.

Start with the business capability and ask: “What is the job this API needs to enable?” A pattern should reflect the domain, not force the domain into a technical shape.

Consumer-centric design.

Choose the pattern that makes intent clearest to your consumers. If the consumer’s job is “cancel an order,” a command is more expressive than a partial update.

Domain-aligned decisions.

The pattern should match the nature of the domain:

  • Is it an entity? CRUD may fit.
  • Is it a workflow step? Extended CRUD or commands may be better.
  • Is it read-optimized? Query model may be needed.
  • Is it a background process? Use async job patterns.

Avoid defaulting to CRUD.

CRUD is not always the right answer — especially in enterprise domains with state transitions, rules, and workflows. Let the domain drive the pattern, not convenience.