Rails is a monolithic Ruby web framework emphasizing convention-over-configuration and rapid development, while FastAPI is a modern Python async framework optimized for API-first development with automatic documentation and high performance. Rails excels at full-stack web applications, whereas FastAPI dominates in building fast REST APIs and microservices.
Rails vs FastAPI — Side-by-side comparison on A Versus B
Full-stack Ruby web framework emphasizing convention over configuration and rapid development.
Modern Python web framework for building APIs with automatic documentation and async support
Performance (Requests/second). Development Speed (time to MVP). Built-in Features. Async Support. Learning Curve. Scalability Model. Ecosystem Maturity
Choose Rails if you're building a traditional full-stack web application, need rapid scaffolding, or require extensive built-in features like authentication, admin panels, and database migrations out-of-the-box. Choose FastAPI if you're prioritizing API performance, building microservices, need native async operations, or prefer modern Python development patterns with automatic interactive documentation.
Ruby on Rails: ~650 req/s | FastAPI: ~18,000 req/s
Ruby on Rails: 18 years (2005) | FastAPI: 6 years (2018)
Ruby on Rails: ~200,000 questions | FastAPI: ~30,000 questions
Ruby on Rails: 1.5 hours (with scaffolding) | FastAPI: 3.5 hours (manual setup required)
Ruby on Rails: Yes (ActiveRecord) | FastAPI: No (requires external library)
Ruby on Rails: Manual (requires Swagger UI gem) | FastAPI: Yes (OpenAPI 3.0)
Ruby on Rails: Limited (background jobs via Sidekiq) | FastAPI: Native (async/await throughout)
Ruby on Rails: ~185,000 gems (RubyGems) | FastAPI: ~480,000 packages (PyPI)
Time to First Deployable Feature (CRUD app)
Ruby on Rails: 150-300 MB | FastAPI: N/A
Ruby on Rails: 2-4 seconds | FastAPI: 300ms
Ruby on Rails: ~8,000 openings | FastAPI: N/A
Ruby on Rails: Airbnb, GitHub, Shopify, Hulu | FastAPI: N/A
Ruby on Rails: 2800ms average | FastAPI: N/A
Ruby on Rails: 60,000 developers | FastAPI: N/A
Ruby on Rails: Yes (ActiveRecord) | FastAPI: N/A
Ruby on Rails: 3000-5000ms (not optimized) | FastAPI: N/A
Ruby on Rails: 12-25 gems | FastAPI: N/A
Ruby on Rails: Server-side only | FastAPI: N/A
Ruby on Rails: 3-4 months | FastAPI: N/A
Ruby on Rails: 55,200 | FastAPI: ~80,000 stars
Ruby on Rails: 18,400 jobs | FastAPI: N/A
Ruby on Rails: 5,000-10,000 | FastAPI: N/A
Ruby on Rails: 120-200 ms | FastAPI: N/A
Ruby on Rails: ~150,000 gems | FastAPI: N/A
Ruby on Rails: Beginner-Friendly (OOP paradigm) | FastAPI: N/A
Ruby on Rails: 200,000+ gems | FastAPI: N/A
Ruby on Rails: ~320 guides | FastAPI: N/A
Ruby on Rails: 55,600 stars | FastAPI: 75,000+
Development Speed (lines of code for basic CRUD)
Ruby on Rails: 200,000 | FastAPI: 500,000+ (PyPI)
Ruby on Rails: Moderate (requires external gems and patterns) | FastAPI: N/A
Ruby on Rails: 8-12 minutes (with scaffolding) | FastAPI: N/A
Ruby on Rails: ActiveRecord (mature, batteries-included) | FastAPI: N/A
Ruby on Rails: Devise gem (built-in pattern) | FastAPI: N/A
Ruby on Rails: Native (views rendered server-side) | FastAPI: N/A
Ruby on Rails: Limited; requires CDN workarounds | FastAPI: N/A
Ruby on Rails: ~1,000 req/s | FastAPI: ~10,000 req/s
Ruby on Rails: ~15 minutes | FastAPI: ~5 minutes
Ruby on Rails: 9 (ORM, routing, auth, migrations, templates, admin, sessions, caching, asset pipeline) | FastAPI: 12 core features
Ruby on Rails: 35,000+ gems | FastAPI: 500,000+ PyPI packages (Python ecosystem)
Ruby on Rails: ~3-5 seconds | FastAPI: 250-500ms
Ruby on Rails: ~18,000 positions | FastAPI: ~12,000 positions
Ruby on Rails: 19 years (released 2005) | FastAPI: 6 years (released 2018)
Ruby on Rails: ~300 req/s | FastAPI: ~7,500 req/s
Ruby on Rails: ~150 MB | FastAPI: ~15 MB
Ruby on Rails: ~30 lines | FastAPI: ~5 lines
Ruby on Rails: Yes (Devise, built-in sessions) | FastAPI: No (requires FastAPI-Users, python-jose)
Ruby on Rails: Yes (ActiveRecord) | FastAPI: No (requires SQLAlchemy, Tortoise-ORM)
Ruby on Rails: ~180,000 gems | FastAPI: ~350,000 PyPI packages (FastAPI-specific: ~4,000)
Ruby on Rails: 1,200-1,800ms (server rendering) | FastAPI: N/A
Ruby on Rails: 4-8 hours (with Rails scaffolding) | FastAPI: N/A
Ruby on Rails: ~18,000 globally (2026) | FastAPI: N/A
Ruby on Rails: N/A (not serverless-native) | FastAPI: N/A
Ruby on Rails: Manual via caching; no native ISR | FastAPI: N/A
Ruby on Rails: 6 (Rails magic can confuse beginners) | FastAPI: N/A
Ruby on Rails: N/A | FastAPI: 8,000-12,000
Ruby on Rails: N/A | FastAPI: No, requires build
Ruby on Rails: N/A | FastAPI: Full native support
Ruby on Rails: N/A | FastAPI: 2,000+ packages
Ruby on Rails: N/A | FastAPI: 22% (Stack Overflow 2024)
Ruby on Rails: N/A | FastAPI: Native (Swagger UI + ReDoc built-in)
Ruby on Rails: N/A | FastAPI: Native (Python type hints)
Ruby on Rails: N/A | FastAPI: Built-in (OpenAPI 3.0)
Ruby on Rails: N/A | FastAPI: Native first-class support
Ruby on Rails: N/A | FastAPI: Python 3.6+
Ruby on Rails: N/A | FastAPI: Automatic (Swagger UI + ReDoc)
Ruby on Rails: N/A | FastAPI: Requires app server (Uvicorn)
Ruby on Rails: N/A | FastAPI: ~2.8M (Jan 2026)
Ruby on Rails: N/A | FastAPI: Yes (Pydantic)
Ruby on Rails: N/A | FastAPI: ~5 minutes
Ruby on Rails: N/A | FastAPI: ~15,000 req/s
Ruby on Rails: N/A | FastAPI: ~1.2M (PyPI: ~2.8M)
Ruby on Rails: N/A | FastAPI: Manual setup required
Ruby on Rails: N/A | FastAPI: Yes (automatic)
Ruby on Rails: N/A | FastAPI: Native, default behavior
Ruby on Rails: N/A | FastAPI: 1,200KB (with uvicorn)
Ruby on Rails: N/A | FastAPI: Native async/await with asyncio
Ruby on Rails: N/A | FastAPI: ~22,000 req/s
Ruby on Rails: N/A | FastAPI: ~400K active
Ruby on Rails: N/A | FastAPI: ~2,500 extensions
Ruby on Rails: N/A | FastAPI: High-level API framework (built on Starlette)
Ruby on Rails: N/A | FastAPI: ~15,000-18,000 req/sec
Ruby on Rails: N/A | FastAPI: Pydantic (integrated)
Ruby on Rails: N/A | FastAPI: ~12,000 req/s
Ruby on Rails: N/A | FastAPI: ~450,000 (PyPI)
Ruby on Rails: N/A | FastAPI: Yes (Pydantic integration)
Ruby on Rails: N/A | FastAPI: Python 3.7+
Ruby on Rails: N/A | FastAPI: 68,000+ stars
Ruby on Rails: N/A | FastAPI: 2.5M weekly
Production Applications (market estimate)
Ruby on Rails: N/A | FastAPI: 45,000+ apps
Ruby on Rails: N/A | FastAPI: ~32,000 req/s
Ruby on Rails: N/A | FastAPI: 30-40 hours
Ruby on Rails: N/A | FastAPI: ~80-120 MB
Ruby on Rails: N/A | FastAPI: Yes (Swagger UI + ReDoc automatic)
Ruby on Rails: N/A | FastAPI: Yes (Pydantic built-in)
Ruby on Rails: N/A | FastAPI: Moderate (3.5/5)
Ruby on Rails: N/A | FastAPI: Full (enforced)
Ruby on Rails: N/A | FastAPI: 150ms (average)
Ruby on Rails: N/A | FastAPI: ~500,000 (PyPI)
Ruby on Rails: N/A | FastAPI: Yes (Swagger/ReDoc)
Ruby on Rails: N/A | FastAPI: ~2.8M (PyPI/month)
Ruby on Rails: N/A | FastAPI: 6 (starlette, pydantic, etc.)
Ruby on Rails: N/A | FastAPI: Native async/await built-in
Ruby on Rails: N/A | FastAPI: 8-10 lines
Production Readiness Without External Server
Ruby on Rails: N/A | FastAPI: Requires ASGI (Uvicorn)
How to choose between Ruby on Rails and FastAPI
Rails vs FastAPI — Structured Comparison Data
Machine-readable comparison dataset for Rails vs FastAPI. Contains 150 attribute comparisons, 5 FAQ pairs.
Rails vs FastAPI — Attribute Category Vocabulary
Taxonomy of attribute categories used to classify comparison data for Rails vs FastAPI.
Can FastAPI replace Rails for full-stack web applications?
Partially. FastAPI is excellent for API backends but lacks Rails' integrated views, form handling, and admin panel. You'd need to add frontend frameworks (React, Vue, Next.js) and additional packages (SQLAlchemy ORM, Alembic migrations, FastAPI-Users for auth). This adds complexity compared to Rails' integrated approach, making Rails still preferable for traditional full-stack monoliths, though FastAPI excels in decoupled API architectures.
Why is FastAPI so much faster than Rails?
FastAPI uses Python's native async/await runtime (asyncio) allowing single-threaded concurrency handling 1000s of concurrent requests. Rails relies on multi-process/multi-threaded models where each request consumes a full process (~150MB), limiting concurrent capacity. FastAPI's lightweight nature and async design yield 25-50x higher throughput on standard hardware.
Is Rails dead? Should I use FastAPI instead?
No. Rails remains production-proven in 150K+ companies and powers major platforms (GitHub, Shopify, Airbnb—originally). Rails dominates monolithic web applications requiring rapid development. FastAPI is newer and optimized for different use cases (APIs, microservices, real-time systems). Choose based on your architecture needs: Rails for traditional full-stack apps, FastAPI for API-centric/microservices.
How difficult is it to learn FastAPI vs Rails?
FastAPI has a gentler learning curve for Python developers. It uses explicit patterns and Python type hints familiar to modern Python ecosystems. Rails requires understanding convention-over-configuration, Rails magic (metaprogramming), and Active Record patterns—steep for beginners but powerful once mastered. Experienced Python developers typically learn FastAPI in 1-2 weeks; Rails takes 3-4 weeks.
Rails typically wins for startups with small teams needing rapid MVP delivery (<4 weeks) and full-stack monoliths. FastAPI wins for startups building API platforms, data services, or planning multi-team microservices from day one. Rails' scaffolding saves weeks; FastAPI's scalability reduces infrastructure costs at higher scale (1000s of requests/second). Choose Rails for speed, FastAPI for growth-phase scaling.
How to Choose Between Ruby on Rails and FastAPI
Performance (Requests/second): Ruby on Rails has ~200-400 req/s, while FastAPI has ~5,000-10,000 req/s.
Consider: Development Speed (time to MVP)
Development Speed (time to MVP): Ruby on Rails has 2-4 weeks, while FastAPI has 1-2 weeks.
Built-in Features: Ruby on Rails has ORM, auth, admin panel, mailers, while FastAPI has Minimal, async-first, docs generation.
Async Support: Ruby on Rails has Limited (background jobs only), while FastAPI has Native async/await throughout.
Learning Curve: Ruby on Rails has Moderate (convention-heavy), while FastAPI has Gentle (explicit, Pythonic).
Scalability Model: Ruby on Rails has Horizontal (stateless instances), while FastAPI has Horizontal + vertical (async multiplexing).
Ecosystem Maturity: Ruby on Rails has 17+ years (est. 1M+ projects), while FastAPI has 6+ years (est. 200K+ projects).