Hire FastAPI Developers · London
Hire FastAPI Developers in London
FastAPI developers for London teams, where mixing synchronous and asynchronous code wrongly is the classic failure. A blocking database call inside an async endpoint stalls the event loop for every concurrent request, the application performs adequately in testing and collapses under load — and the code looks entirely reasonable.
Why this comes up
The problem
Async endpoints make blocking calls and throughput falls apart as soon as traffic arrives.
What you get
What we deliver
- Understanding of what blocks the event loop tested directly
- Async and sync endpoint choice discussed, since both are valid in different places
- Database driver awareness confirmed, as this is where blocking usually enters
- Pydantic model competence assessed, given how central validation is to the framework
- Dependency injection experience probed where your application uses it
- Load behaviour understanding valued, because the failure only appears under concurrency
Want this scoped for your business in London?
Thirty minutes, no charge, no sales script. You leave with a written summary of what hire fastapi developers would actually involve — whether or not you use us.
Working in London
London
London clients usually come to us because they want senior people actually on their project rather than a large agency's B team, and because Midlands rates buy considerably more delivery per pound.
Clients here are usually replacing an agency, and want senior people on the work at rates that are not Central London rates.
Sectors we work with in London
- Financial Services
- Professional Services
- Technology
- Media
- Hospitality
- Retail
What we work with
Technologies and platforms
- FastAPI
- Python
- Pydantic
- PostgreSQL
Who we work with
Industries we serve
- SaaS businesses
- Technology companies
- Financial services
- Healthcare
- Startups
Why us
Why London businesses choose Asionis
- Projects typically launched within 4–8 weeks
- No long-term contracts required
- All team members UK-based
- Dedicated account manager and development team
- Transparent reporting with monthly performance metrics
- Scalable from startup to enterprise
How we work
- Step 1
Free consultation
A 30-minute call to understand the problem. You keep the written summary either way.
- Step 2
Proposal
Scope, timeline and a fixed price, in writing, before anything starts.
- Step 3
Build
Short cycles with regular check-ins, so you see progress rather than hear about it.
- Step 4
Launch and support
We handle the go-live and stay available afterwards.
Other services in London
Looking for the full picture? See our Hire FastAPI Developers services, everything we do in London or browse everything we do.
Hire FastAPI Developers in London — common questions
- Why is mixing sync and async dangerous?
- Because a blocking call inside an async function holds the event loop. Every other request waits, so an application that responds fine to one user at a time degrades sharply under concurrency — and nothing in development reveals it.
- Should everything be async?
- No, and the framework supports both deliberately. A synchronous endpoint runs in a thread pool and is entirely appropriate where the work is blocking, so the correct answer depends on the operation — which is exactly the judgement worth testing.
- Where does blocking usually enter?
- The database driver. A synchronous library used inside an async endpoint is the most common cause, and it requires knowing which driver you are using rather than assuming that because the framework is async everything beneath it is too.
- How central is Pydantic?
- Very. Request and response validation, serialisation and the generated documentation all flow from the models, so somebody comfortable defining them well produces clearer APIs — and somebody who bypasses them loses most of what the framework offers.
- Do you work with businesses across Greater London?
- Yes. We are based in Leicester, United Kingdom and work with clients throughout London, including London and the surrounding Greater London area. Most collaboration happens remotely, and we travel for kick-offs and key milestones.
- What kind of London businesses do you usually work with?
- Clients here are usually replacing an agency, and want senior people on the work at rates that are not Central London rates. Beyond that we work across Financial Services, Professional Services, Technology, Media, Hospitality and Retail.
- Do you cover the areas around London?
- Yes — we work throughout London, including Reading, Milton Keynes, Cambridge, Brighton. London is an urban area of roughly 9,000,000+, and we take on work across the wider Greater London region rather than the city boundary alone.
Talk to us about Hire FastAPI Developers in London
A 30-minute call with someone who would actually work on it. No sales script, no obligation.
- Projects typically launched within 4–8 weeks
- No long-term contracts required
- All team members UK-based
- Dedicated account manager and development team
- Transparent reporting with monthly performance metrics
- Scalable from startup to enterprise