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Skill Guide

API design and development (REST/GraphQL)

The systematic process of architecting, defining, and implementing interfaces that enable software systems to communicate and exchange data, with REST using stateless, resource-oriented HTTP calls and GraphQL offering a flexible, client-driven query language.

This skill directly enables scalable system integration, accelerates product development through decoupled services, and is fundamental to building modern microservices architectures and data-driven applications. Proficiency here reduces technical debt, improves developer experience, and directly impacts time-to-market and system reliability.
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1 Categories
9.1 Avg Demand
15% Avg AI Risk

How to Learn API design and development (REST/GraphQL)

1. Grasp core HTTP methods (GET, POST, PUT, DELETE, PATCH) and status codes; 2. Understand JSON/XML data formats and basic schema design; 3. Practice designing simple CRUD endpoints for a resource (e.g., /users, /products) using a tool like Postman.
1. Implement authentication/authorization (OAuth2.0, JWT); 2. Design for pagination, filtering, and partial responses; 3. Avoid N+1 query problems and learn caching strategies (ETags, Cache-Control). Common mistake: Ignoring backward compatibility when versioning APIs.
1. Architect API-first strategies for large-scale microservices; 2. Design and enforce API governance (style guides, contract testing with Pact); 3. Optimize for performance and resilience using patterns like circuit breakers and implementing robust observability (distributed tracing).

Practice Projects

Beginner
Project

Build a Personal Blog REST API

Scenario

You need to create a backend API for a simple blog application where users can create, read, update, and delete posts and comments.

How to Execute
1. Define resources (Post, Comment) and map CRUD operations to HTTP verbs and endpoints (e.g., GET /posts/{id}); 2. Use a framework like Express.js (Node.js) or Flask (Python) to implement the endpoints and connect to a SQLite database; 3. Test all endpoints and edge cases (404, validation errors) using Postman; 4. Document the API endpoints using OpenAPI/Swagger.
Intermediate
Project

Extend an E-commerce API with GraphQL and Auth

Scenario

Your existing REST API for an e-commerce platform needs a flexible data-fetching layer for the mobile frontend and must securely handle user sessions and orders.

How to Execute
1. Set up a GraphQL server (e.g., Apollo Server) alongside or replacing key REST endpoints; 2. Define a schema with types for Product, User, Order, and queries/mutations for common operations; 3. Implement resolver functions that efficiently fetch and combine data from multiple data sources; 4. Add JWT-based authentication middleware and secure specific mutations (e.g., placeOrder).
Advanced
Project

Design and Implement an API Gateway for Microservices

Scenario

Your company is decomposing a monolith into microservices. You need to design a unified API gateway that handles routing, aggregation, rate limiting, and authentication for a complex set of backend services.

How to Execute
1. Analyze client requirements and design a cohesive API facade (considering BFF pattern for different clients); 2. Select and configure a gateway technology (Kong, AWS API Gateway, a custom Node.js service); 3. Implement cross-cutting concerns: request routing, authentication/authorization, request/response transformation, and rate limiting; 4. Integrate observability tools (OpenTelemetry) and establish CI/CD pipelines for gateway configuration.

Tools & Frameworks

Software & Platforms

PostmanOpenAPI (Swagger)GraphQL Playground

Postman is essential for manual testing and automation of REST APIs. OpenAPI is the industry standard for defining, documenting, and generating REST API contracts. GraphQL Playground is the interactive IDE for exploring and testing GraphQL schemas and queries.

Frameworks & Libraries

Express.js (Node.js)FastAPI (Python)Apollo Server (GraphQL)NestJS

Express and FastAPI are dominant frameworks for building performant REST APIs. Apollo Server is the leading library for building a GraphQL server. NestJS provides a structured, Angular-like architecture for building scalable server-side applications with built-in support for both REST and GraphQL.

Testing & Quality

Pact (Contract Testing)Jest/Mochak6 (Performance Testing)

Pact enables consumer-driven contract testing to ensure APIs meet client expectations without integration tests. Jest/Mocha are standard unit/integration testing frameworks. k6 is used for load testing and performance benchmarking API endpoints.

Interview Questions

Answer Strategy

The interviewer is testing knowledge of API evolution and backward compatibility. Use the STAR method to structure your answer, focusing on practical implementation. 'I'd recommend URL path versioning (e.g., /v1/users) for its explicitness and cacheability, accepting the maintenance of multiple versions. For less breaking changes, header-based versioning (Accept header) can be cleaner but adds complexity. A key trade-off is simplicity for developers versus long-term maintenance burden.'

Answer Strategy

Tests system design thinking and ability to manage stakeholder expectations. The core competency is understanding performance implications and educating on best practices. 'My primary concern is the potential for expensive, deeply nested queries that could overload the database, especially for unauthenticated clients. I'd advise implementing persisted queries for production, setting query depth/cost limits, and using DataLoader to batch and cache database requests. We should collaborate to define a schema that balances flexibility with performance guardrails.'

Careers That Require API design and development (REST/GraphQL)

1 career found