express vs fastify

backend

express

fastify

Express and Fastify are both Node.js web frameworks for building backend APIs and web applications. Express, released in 2010, is the de facto standard framework with a callback-based architecture and the largest ecosystem in the Node.js world. Fastify, launched in 2016, is a modern alternative built from the ground up for speed, using async/await patterns and schema-based validation to deliver 2-3x better performance than Express.

This comparison matters because choosing between them involves real trade-offs between ecosystem maturity and raw performance. Express targets developers who prioritize stability, extensive middleware availability, and community resources. Fastify appeals to teams building high-performance systems, microservices architectures, or new projects where modern async patterns and built-in validation are valuable. Both are production-ready, but serve different priorities.

Head-to-Head

Request Throughput→ fastify wins

express

Handles 20,000-27,000 requests per second in benchmarks. Sufficient for most applications but shows limitations under heavy load due to callback-based overhead and less efficient routing.

fastify

Handles 48,000-76,000 requests per second—roughly 2-3x faster than Express. Uses 'find-my-way' router (3x faster routing) and schema-based JSON serialization for superior throughput.

Memory Efficiency→ fastify wins

express

Consumes approximately 150 MB at 10,000 concurrent connections. Mutable req/res objects and middleware chain create more overhead per request.

fastify

Uses approximately 100 MB at 10,000 concurrent connections. Immutable request/response objects and optimized architecture reduce memory footprint by ~33%.

Middleware Ecosystem→ express wins

express

Massive ecosystem with thousands of middleware packages covering every conceivable use case. Mature solutions exist for authentication, validation, logging, rate limiting, and more.

fastify

Growing but significantly smaller plugin ecosystem. Many Express middleware can be adapted, but requires more custom implementation for edge cases.

Schema Validation→ fastify wins

express

No built-in validation. Requires third-party libraries like Joi, express-validator, or Yup. Adds boilerplate and requires manual integration with routing.

fastify

Built-in JSON Schema validation for request/response. Validates and serializes automatically, reducing boilerplate and improving performance through schema compilation.

TypeScript Integration→ fastify wins

express

Requires @types/express and additional configuration. Type inference for request/response needs manual typing. Community types are comprehensive but sometimes lag behind releases.

fastify

Better native TypeScript support with easier type inference. Generic types for request/response objects work more naturally with async/await patterns.

Learning Curve→ express wins

express

Simpler mental model with mutable objects and straightforward middleware chain. Abundant tutorials, Stack Overflow answers, and learning resources. Easier onboarding for junior developers.

fastify

Requires understanding schemas, immutable objects, and plugin architecture. Smaller community means fewer tutorials and Stack Overflow answers. Steeper initial learning curve.

Verdict

Choose Fastify if you're starting a new project where performance matters, building microservices, or working with TypeScript. The 2-3x performance improvement is real and measurable, the built-in schema validation eliminates boilerplate, and the modern async/await architecture will age better than Express's callback heritage. The smaller ecosystem is a trade-off worth making for systems that need to handle significant traffic or where response latency directly impacts user experience.

Choose Express if you're working on an existing Express codebase, building a project where extensive third-party integrations are critical, or prioritizing team velocity with junior developers. The performance difference won't matter for most CRUD APIs serving moderate traffic, and the ecosystem advantage is substantial—you'll find pre-built solutions for almost everything. Express 5's recent release shows the project is still maintained, though its fundamental architecture remains callback-based. For typical web applications with standard traffic patterns, Express's maturity outweighs Fastify's speed.

When to Use Each

If you are building a high-traffic API serving millions of requests per day → use Fastify because the 2-3x throughput improvement directly reduces infrastructure costs and improves response times at scale.

If you are building a standard CRUD application with moderate traffic (< 1000 req/min) → use Express because the performance difference is negligible at this scale and you'll benefit more from the massive middleware ecosystem.

If you are building microservices that need schema validation and service-to-service communication → use Fastify because built-in JSON Schema validation reduces boilerplate and the performance gains compound across multiple services.

If you are maintaining an existing Express application or working with a team unfamiliar with modern async patterns → use Express because migration costs outweigh performance benefits and the learning curve could slow development velocity.

Learn More

express →fastify →

Head-to-Head

Request Throughput→ fastify wins

express

Handles 20,000-27,000 requests per second in benchmarks. Sufficient for most applications but shows limitations under heavy load due to callback-based overhead and less efficient routing.

fastify

Handles 48,000-76,000 requests per second—roughly 2-3x faster than Express. Uses 'find-my-way' router (3x faster routing) and schema-based JSON serialization for superior throughput.

Memory Efficiency→ fastify wins

express

Consumes approximately 150 MB at 10,000 concurrent connections. Mutable req/res objects and middleware chain create more overhead per request.

fastify

Uses approximately 100 MB at 10,000 concurrent connections. Immutable request/response objects and optimized architecture reduce memory footprint by ~33%.

Middleware Ecosystem→ express wins

express

Massive ecosystem with thousands of middleware packages covering every conceivable use case. Mature solutions exist for authentication, validation, logging, rate limiting, and more.

fastify

Growing but significantly smaller plugin ecosystem. Many Express middleware can be adapted, but requires more custom implementation for edge cases.

Schema Validation→ fastify wins

express

No built-in validation. Requires third-party libraries like Joi, express-validator, or Yup. Adds boilerplate and requires manual integration with routing.

fastify

Built-in JSON Schema validation for request/response. Validates and serializes automatically, reducing boilerplate and improving performance through schema compilation.

TypeScript Integration→ fastify wins

express

Requires @types/express and additional configuration. Type inference for request/response needs manual typing. Community types are comprehensive but sometimes lag behind releases.

fastify

Better native TypeScript support with easier type inference. Generic types for request/response objects work more naturally with async/await patterns.

Learning Curve→ express wins

express

Simpler mental model with mutable objects and straightforward middleware chain. Abundant tutorials, Stack Overflow answers, and learning resources. Easier onboarding for junior developers.

fastify

Requires understanding schemas, immutable objects, and plugin architecture. Smaller community means fewer tutorials and Stack Overflow answers. Steeper initial learning curve.

Verdict

When to Use Each