Careful with money
Money is stored as whole numbers, and a payment retry can never charge anyone twice.
Open to engineering roles & freelance projectsHi, I’m Seun.
Hi, I’m Seun.
Software engineer in Lagos.
I specialise in the backend, writing Rust, Java and Node services, payment flows and ledgers. I also design and build the web and mobile apps that use them, and I keep them running after launch.
Lagos, NigeriaWAT (GMT+1) · remote or relocation
- 89k
- conversations I fine-tuned a model on
- 460
- commits to Sayfi since late September
- 350+
- Rust tests in Sayfi’s engine
- 3 days
- from first commit to a live store for OT Collectives
How I work
I design and I build
I design the screens myself, so what you approve is what goes live.
Code someone else can pick up
I write typed code with tests and docs and keep a clean commit history, so another engineer can take over without me.
Recent work
- Aug 2026 – Now
Founder & software engineer · Sayfi
- Wrote the trading engine in Rust (Tokio, gRPC). It simulates every transaction and blocks instructions the user didn’t ask for.
- Designed a double-entry ledger in PostgreSQL that is append-only, uses idempotency keys and stores money as integers.
- Fine-tuned Qwen 2.5 14B on 89,000 conversations and serve it on a GPU, with its output locked to a schema.
- Feb 2026 – Now
Full-stack engineer, mobile & backend · Call Lawya
- Built the iOS and Android app in React Native and Expo. It’s on both stores and now on version 2.1.
- Built the backend in NestJS and Prisma on Azure. It handles bookings, Paystack payments, weekly payouts, chat and voice calls.
- Made chat work offline with SQLite, and wrote the call signalling so calls hold up on weak networks.
- 2026 – Now
Freelance software engineer · made by seun
- Designed and built the OT Collectives Atelier store with Paystack payments in under a week.
- Design, build and deploy each project, and support it after launch.
Skills
Languages
- TypeScript
- Java
- Rust
- JavaScript
- SQL
- Python
Backend & systems
- Java
- Rust
- Node.js
- NestJS
- Tokio
- gRPC
- REST
- WebSockets
- Prisma
- SQLx
Payments & money
- Paystack
- Webhooks (HMAC)
- Double-entry ledgers
- Idempotency
- Reconciliation
Data
- PostgreSQL
- Row-level security
- Supabase
- SQLite
- Redis
Frontend & mobile
- React
- Next.js
- React Native
- Expo
- Tailwind CSS
Cloud & delivery
- Docker
- Azure
- Google Cloud
- Vercel
- GitHub Actions
- Sentry