Technology

FastAPI: Fast, secure APIs for your web application

REST APIs, webhook handlers, data processing, AI integrations — when your project needs a powerful backend, we build with FastAPI. Python's fastest web framework.

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Simply explained

What is FastAPI?

FastAPI is a modern Python framework for building APIs — the invisible interfaces through which your website, app, or AI systems exchange data. Created by Sebastian Ramirez, it is one of the fastest-growing web frameworks today.

Simply put: When your frontend (the website your customers see) needs data — prices from a database, a booking confirmation, or an AI response — FastAPI provides that data. Fast, secure, and reliable.

What makes FastAPI special: it automatically generates interactive API documentation (OpenAPI/Swagger), validates all inputs with Pydantic, and thanks to async/await is as fast as Node.js — with the readability of Python.

For you as a business owner, this means: a backend that grows with you. Whether 100 or 100,000 requests per day — FastAPI scales with your business and can be extended with AI features at any time.

Use cases

What we use FastAPI for

FastAPI is not the right choice for every project — but when Python's strengths are needed, there is hardly anything better.

REST APIs

CRUD operations, data queries, form processing — the foundation of every web application.

Webhook handlers

Stripe payments, email events, CRM updates — external services send data, FastAPI processes it.

AI integrations

OpenAI, Langchain, Hugging Face — Python is the language of AI. FastAPI connects your app with LLMs and ML models.

Data processing

CSV imports, PDF generation, reporting — Python excels at data processing, FastAPI makes it accessible.

Typical setup: Astro or Next.js as the frontend, FastAPI as the backend, Supabase or PostgreSQL as the database. Three technologies, perfectly aligned — each doing what it does best.

Why FastAPI

6 benefits for your backend

Async Performance

Thanks to async/await, FastAPI efficiently handles thousands of concurrent requests. Performance on par with Node.js and Go — in readable Python code.

Auto Documentation

Every endpoint is automatically documented as an interactive Swagger UI. Developers can test your API directly in the browser — no Postman or extra tools needed.

Type Safety

Pydantic validates every input automatically. Wrong data types, missing fields, invalid values — everything is caught before it causes damage.

Python Ecosystem (AI/ML)

Access to numpy, pandas, scikit-learn, OpenAI, Langchain, and thousands more Python libraries. Ideal when your project needs AI or data features.

Easy Testing

FastAPI has a built-in test client. Every endpoint can be automatically tested — for reliable code that remains stable even after updates.

FastAPI + Astro/Next.js

Perfect complement to our frontend frameworks. FastAPI delivers the data, Astro or Next.js displays it. Clean separation, maximum flexibility.

Our process

How we build your API

Structured and test-driven — so your backend stands on solid ground from the start.

API design & schema

We define your endpoints, data models, and authentication. You receive an OpenAPI specification before a single line of code is written.

Database & models

We structure your database with SQLAlchemy or Prisma, create migrations, and ensure clean relationships between your data.

Development & testing

Every endpoint is secured with automated tests. You can test the API live via Swagger UI and give feedback — while development is still ongoing.

Deployment & monitoring

Your API is deployed on scalable cloud infrastructure. With health checks, logging, and alerting — so problems are detected before your users notice them.

FAQ

Frequently asked questions about FastAPI

How much does FastAPI development cost?

Professional FastAPI backend development from 0gravity starts at CHF 4,900. The price depends on scope: number of endpoints, database structure, authentication, external integrations, and deployment requirements. Simple REST APIs with a few endpoints start lower.

Why Python instead of Node.js for the backend?

Python is the dominant language for data processing, machine learning, and AI integrations. If your project uses OpenAI, Langchain, or other AI services, Python is the natural choice. For pure JavaScript stacks or real-time WebSocket applications, we recommend Node.js.

Is FastAPI secure enough for production systems?

Yes. FastAPI uses Pydantic for automatic data validation — every input is checked against a schema before processing. Add OAuth2/JWT authentication, CORS configuration, and automatic SQL injection prevention through SQLAlchemy. Microsoft, Uber, and Netflix use FastAPI in production.

How is a FastAPI application hosted?

Most commonly on cloud platforms like Railway, Fly.io, or AWS. For serverless deployments, AWS Lambda or Google Cloud Functions work well. Hosting costs start at CHF 0/month for small APIs and scale with traffic.

Can FastAPI communicate with my Astro/Next.js frontend?

Absolutely. FastAPI provides a REST API with automatic OpenAPI documentation by default. Your frontend — whether Astro, Next.js, or a mobile app — communicates via HTTP requests. We configure CORS, authentication, and data formats cleanly for your project.

How long does FastAPI API development take?

A simple REST API with 5–10 endpoints is achievable in 1–2 weeks. More complex backends with authentication, database migrations, external integrations, and webhook processing require 3–6 weeks. AI integrations with RAG or LLM pipelines: 4–8 weeks.

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