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FastAPI Development
Typed, async Python APIs with validation and documentation generated from the code, often serving ML models.
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What FastAPI is
FastAPI is a Python web framework for building APIs. You declare request and response shapes with Python type hints and Pydantic models, and it validates input, serialises output and generates OpenAPI documentation from those same declarations.
It is built on async Python, so it handles many concurrent I/O-bound requests well. It is deliberately an API framework, not a full-stack one: there is no ORM, admin or templating story built in, and you choose those pieces yourself.
Suitability
And when it is not. Choosing the wrong tool costs more than any implementation detail.
Good fit for
- APIs that wrap or serve machine learning and data-science code written in Python
- Services where a precise, self-documenting contract matters, such as APIs consumed by several client teams
- Python teams wanting async performance without leaving the language
- Lean microservices with a clearly bounded responsibility
Consider alternatives for
- Applications that need an admin interface, built-in auth and ORM out of the box — Django is faster to a working product
- Teams that are TypeScript-first, where a Node.js service shares types with the frontend directly
- CPU-bound endpoints inside the event loop, which block every other request just as in any async runtime
In practice
01
ML and LLM serving
Wrapping a model or an LLM pipeline in a typed endpoint with validation, streaming responses and clear timeouts.
02
Typed service APIs
Contract-first services where the generated OpenAPI spec is the documentation other teams build their clients from.
03
Data and integration endpoints
Small services that expose a data pipeline or an internal Python library over HTTP without dragging in a full framework.
Considerations
Practical notes from running this in production.
- 01
Async only helps if everything in the path is async. One blocking database driver or library call inside an async endpoint stalls the whole worker, a failure that load testing finds and unit tests do not.
- 02
Heavy model inference should not run on the event loop. It belongs in a thread pool, a separate worker process or a dedicated inference service, with the API only orchestrating.
- 03
Pydantic validates shape, not business rules or authorisation. Permissions still need explicit checks in every route or a shared dependency.
- 04
Because the framework is thin, project structure is your job. We set conventions for routers, dependencies and settings early so the codebase does not drift.
FAQ
Is FastAPI faster than Django or Node.js?
For I/O-bound work it is comparable to other async frameworks, and well ahead of a synchronous Django view under high concurrency. In most real systems the database or a downstream call dominates latency, so the framework is rarely the deciding factor. Pick it for its typing and ergonomics, not a benchmark.
Do you have production experience with FastAPI?
Our primary backend stacks are Node.js (with NestJS and Express) and Python with Django. FastAPI is a framework we take on per engagement, mainly where a project is Python-based and API-shaped. We will tell you plainly at the start if a different choice would serve you better.
Can FastAPI replace a Django project?
Only if the Django parts you rely on, such as the admin, ORM and authentication, are replaceable in your case. Moving a full Django application to FastAPI usually means rebuilding those layers, which is rarely worth it unless the workload has genuinely become API-and-throughput-bound.
How long does a FastAPI development project take?
It depends on scope. A focused first release is usually weeks rather than months, while larger platforms are delivered in phases. We give a written estimate after a short discovery conversation and agree milestones before work starts.
How is FastAPI development work priced?
We work either to a fixed scope with agreed milestones or on a time-and-materials basis, whichever suits how well the requirements are known. You receive the estimate and its assumptions in writing before committing.
By industry
Where we apply FastAPI. Tiles marked "Guide" open a dedicated write-up; the rest open the industry page.
Let’s talk about your FastAPI project
Tell us what you are trying to build or fix. We will come back with scope, approach and an honest view on cost and timeline.