Open to full-stack engineering roles
Liyona Johny
Full-Stack Software Engineer
I build the API and the interface that sits on top of it, then ship the whole thing.
Five years across Python, FastAPI and React, most recently on an enterprise digital twin platform in Edinburgh. Now freelance in the US, building client applications and the occasional security review. Authorized to work in the US, no sponsorship needed.
FastAPI + React
- Years of engineering experience
- 5+
- Projects written up, with the code public where it can be
- 10
- Fewer P1 incidents over two quarters at Infosys
- 20%
- Endpoints documented in OpenAPI and handed over
- 100%
How I work
Four things you can check rather than take on trust
Every claim on this page is one you can verify, either in the code I hand over or in this site itself.
-
Security is part of the build
JWT authentication, role-based access, audit logging, and CORS policy across both API and UI, not bolted on afterwards.
-
Tested the way it will be attacked
Automated coverage and peer review, then a manual pass over access control, data isolation, and payment flows before release.
-
Documented for handover
Every endpoint in OpenAPI, and system behaviour written up in language non-engineers can use without me in the room.
-
No tracking on this site
No analytics, no cookies, no third-party scripts. The contact form is the only thing that ever sends data anywhere.
PageSpeed, mobile
This site, measured on the live URL. Proof of the work rather than a claim about it.
See the full reportWhat I do
The whole stack, not half of it
I work across the whole stack. On the backend that usually means Python with FastAPI or Django, SQLAlchemy and Pydantic for modelling and validation, and PostgreSQL or MySQL underneath. On the front end it means React with hooks and context, or Astro when a site has to be fast and search friendly above everything else.
Most of my work starts with an open-ended conversation rather than a written spec. I'm comfortable sitting with clients and researchers who are not engineers, turning what they describe into a data model, an API surface, and an interface they can actually use, then documenting it in language they can rely on long after handover.
I use AI coding tools every day, and I review and test what they produce to exactly the same standard as code I write by hand.
More about how I work-
API design that holds up
Typed request and response models, validation on ingest, and every endpoint documented in OpenAPI so the people consuming it never have to guess.
-
Front ends that match the contract
Component architecture and state management in React, with behaviour verified against the API contract before anything reaches release.
-
Security built in, not bolted on
JWT authentication, role-based access control, protected routes, session handling, audit logging, and CORS policy across both API and UI, then tested from the outside to confirm it holds.
-
Performance as a requirement
Core Web Vitals budgets, technical SEO, structured data, and accessibility treated as acceptance criteria rather than a later clean-up pass.
Selected work
Work worth reading about
Each of these has a full write-up covering the problem, the constraints, the decisions, and what I would change.
-
Digital Twin Platform
2023 to 2025
Santane Ltd
Real-time simulation and analytics platform managing live data streams, validating every input on ingest and delivering processed output to the interface.
- FastAPI services and React interfaces that visualize live twin data.
- JWT authentication and role-based access control across both API and UI.
- AWS environments provisioned and operated with Docker, Git, and Jenkins pipelines.
- Each role tested against the API directly, so access rules were proven rather than assumed.
Read the case study
-
ClinicalPilot AI
2025 to 2026
AI-powered clinical research platform, MCA major project
A research platform that ingests FHIR R4 and C-CDA records, runs retrieval over the literature, and answers questions about both through a streaming agent.
- Ingests FHIR R4 and C-CDA clinical data, validated and profiled before anything reaches analysis.
- Retrieval over papers with pgvector, and a streaming agent with three tools answering across both.
- A twenty-question evaluation harness, so a change to the prompt or the retrieval is measured rather than eyeballed.
- 159 tests, including validation exercised against deliberately broken datasets.
Read the case study
-
Freelance client build
A scheduling and administration platform for a music school, with family accounts, moderated messaging, live lessons in the browser, and SMS reminders that arrive.
- Scheduling, family accounts, and moderated messaging between staff and families.
- Live lessons over WebRTC, with WebSockets carrying presence and messages as they happen.
- SMS through Twilio for the reminders that have to arrive, and role-based access with audit logging.
- Single sign-on into LearnDash so students move between systems without a second login.
- Family data isolation tested at the API before handover, with findings ranked by severity.
Read the case study
Writing
Notes from the work
Practical guides on API design, security, performance, and testing. Written from things I have actually had to get right.
-
Writing MCP tools an agent picks correctly
The tool name, description and schema are the interface. What the protocol guarantees, what it only hints at, and why the server still has to check everything.
Read it
-
What to do about a webhook that arrives twice
Duplicate deliveries, no ordering guarantee, and a signature you have to check yourself. The handler shape that survives all three.
Read it
-
The PyTest fixtures worth writing on day one
Four fixtures that make an API test suite fast, isolated, and pleasant to add to, with the database rollback pattern in full.
Read it
Next step
Looking for someone to own this end to end?
I am open to full-stack engineering roles and to contract builds. Tell me what you are trying to solve and I will tell you honestly whether I am the right person for it.
- Replies: Within two working days
- Based in: the United States
- Open to: full time, contract, remote or hybrid