Framework Comparison

    ExpressvsFastify

    Performance benchmarks, features, and migration guide. Fastify delivers 3-4x higher throughput than Express.

    No data stored. No training on your code.
    Performance Benchmarks

    Real-World Performance Metrics

    Comparing Express.js and Fastify under production load

    4x
    Requests/sec
    Express:~15,000
    Fastify:~60,000
    4x faster
    Latency (p99)
    Express:~8ms
    Fastify:~2ms
    ~30% less
    Memory Usage
    Express:Higher
    Fastify:Lower
    2.5x faster
    Startup Time
    Express:~50ms
    Fastify:~20ms

    Fastify is 3-4x Faster

    In production environments, Fastify consistently handles 3-4x more requests per second than Express, with lower latency and memory usage. These performance gains are especially noticeable under high load.

    How It Works

    How Refactyl Migrates Express → Fastify

    A simple, transparent process that reduces fear and builds confidence

    01

    Scan

    Parse routes, middleware, plugins, and configs

    02

    Transform

    Convert routing, validation, async handlers, plugins

    03

    Validate

    Type-safe output + schema checks

    04

    Review & Export

    Clean diff, ready-to-commit code

    See the Transformation

    Developers Trust Code, Not Copy

    Here's what your Express code becomes

    Before

    Express.js

    routes/users.js
    const express = require('express');
const app = express();

app.get('/users', (req, res) => {
  const { page, limit } = req.query;
  res.json({ users });
});

app.post('/users', (req, res) => {
  const user = req.body;
  // No validation
  res.status(201).json({ user });
});
    After

    Fastify + TypeScript

    routes/users.ts
    TypeScript
    import Fastify from 'fastify';
const app = Fastify({ logger: true });

app.get<{
  Querystring: { page?: number; limit?: number }
}>('/users', async (request) => {
  const { page, limit } = request.query;
  return { users };
});

app.post<{
  Body: { name: string; email: string }
}>('/users', async (request) => {
  // Automatic validation via schema
  return { user: request.body };
});
    Full TypeScript inference
    Automatic schema validation
    Native async/await patterns
    Feature Comparison

    Side-by-Side Comparison

    See how Express.js and Fastify stack up across key features

    FeatureExpress.jsFastifyWinner
    PerformanceGoodExcellent (3-4x faster)
    Fastify
    TypeScript SupportCommunity packagesNative, built-in
    Fastify
    Schema ValidationRequires middleware (Joi, Yup)Built-in JSON Schema
    Fastify
    Plugin ArchitectureMiddleware-basedPlugin-based with isolation
    Fastify
    Async/AwaitCallback-based (legacy)Native async/await
    Fastify
    EcosystemLargest (most packages)Growing rapidly
    Express
    Learning CurveEasier (more tutorials)Slightly steeper
    Express
    Request ValidationManual or middlewareAutomatic via schemas
    Fastify
    LoggingRequires middleware (Winston, Pino)Built-in Pino logger
    Fastify
    HTTP/2 SupportLimitedFull support
    Fastify
    What We Handle

    What Refactyl Handles

    Answering the silent question: "Will this handle my mess?"

    Routes & Controllers
    Middleware → Plugins
    Validation (Joi → JSON Schema)
    Auth & Guards
    Async error handling
    TypeScript conversion
    Monorepos
    Custom edge cases flagged
    Safe by Design

    Migration = Risk. We've Built Safety In.

    Every step designed to protect your code and your peace of mind

    No code executed

    Refactyl analyzes and transforms code—it never runs your application code.

    No production access

    We never need access to your production environment or databases.

    No vendor lock-in

    You own 100% of the output. Standard Fastify code, no proprietary formats.

    Full transparency

    See exactly what changes before committing. Clean, reviewable diffs.

    Is Refactyl Right for You?

    Honesty Converts Better

    Here's who we're built for—and who might want to wait

    Refactyl is for

    • Production Express APIs
    • Teams migrating to Fastify seriously
    • TypeScript-first backend teams
    • Large codebases & monorepos
    • Teams wanting clean, reviewable migrations

    Not ideal if

    • Toy projects or simple demos
    • Heavy custom C++ addons
    • Non-Node.js backends
    • Teams not ready for TypeScript
    • One-off scripts or utilities

    Frequently Asked Questions

    Objection-handling questions about migration safety, accuracy, and process.

    No. Refactyl ensures zero breaking changes. All routes, middleware, and functionality are preserved. The migration converts Express patterns to Fastify equivalents while maintaining identical application logic. You get clean, reviewable diffs before committing anything.
    Minimal. Refactyl handles 95%+ of the migration automatically, including routes, middleware conversion, TypeScript types, and validation schemas. You'll need to review the generated code (which we make easy with clean diffs) and test your application—standard practice for any migration.
    Yes. Refactyl works with private repositories. Your code is processed in isolated Docker containers and automatically deleted within 7 days. We never store your code permanently or use it for training. Your code belongs to you.
    Custom middleware is converted to Fastify hooks and plugins. Refactyl intelligently maps Express middleware patterns to Fastify equivalents. Edge cases are flagged (not broken) so you can review and adjust as needed. Most common middleware patterns are fully automated.
    Very accurate. Refactyl uses advanced AI to understand your codebase structure and patterns. Typical migrations achieve 95%+ accuracy on first pass, with the remaining edge cases clearly flagged for review. You always see exactly what changed before committing.
    Yes. You can re-run migrations as your codebase evolves. Refactyl tracks changes and can incrementally update your Fastify codebase. This is especially useful for large codebases where you might migrate in phases.

    Migrate with Confidence

    See exactly what changes—before committing anything. Clean diffs, zero breaking changes, production-ready output.