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Hi there, I’m

David Belykh

Java full-stack engineer building dependable backends and the interfaces on top of them.

I work across the stack, from Java services and data pipelines to Vue and plain JavaScript frontends. Lately: healthcare interoperability with HL7 FHIR, load balancing in Go, and putting LLMs to work inside small, useful tools.

See my work GitHub

A bit about me

I like systems you can reason about: clear data flows, boring infrastructure, and code that the next person can pick up without a guided tour.

Most of my day is Java — services, APIs and the plumbing between them. On the side I use small projects to learn things properly: writing a load balancer from scratch in Go to understand health checks and request routing, wiring an LLM into a chess board so it can actually see the position, or building a HAPI FHIR server with an ingestion pipeline that turns messy clinical files into clean transaction bundles.

I care about the unglamorous parts: logging that helps at 3 a.m., Docker setups that start on the first try, and READMEs that tell you how to run the thing.

Things I've built5

  • Java · 2026

    HAPI FHIR Server

    An HL7 FHIR R4 server with an automated pipeline that ingests clinical files into PostgreSQL.

    A HAPI FHIR server for HL7 FHIR R4, paired with a Python ingestion pipeline. The pipeline watches an input folder, normalises incoming clinical resources and posts them as FHIR transaction Bundles, so data lands in PostgreSQL through the server's own validation instead of around it.

    The interesting part is the unhappy path: files that fail validation are moved to an error folder with logs that say why, processed files are archived, and the whole stack comes up with a single docker compose up.

    • Continuous folder-watching ingestion with processed / error separation
    • Resources sent as FHIR transaction Bundles for atomic writes
    • One-command local stack with Docker Compose
    • Java
    • HAPI FHIR
    • Python
    • PostgreSQL
    • Docker
    1

  • JavaScript · 2025

    Chess × LLM

    A two-player chess board with an AI assistant that can actually see the position.

    • JavaScript
    • TypeScript
    • Cloudflare Workers AI
    • SSE

  • Go · 2026

    LoadBalancer

    A load balancer written from scratch in Go to learn how request routing really works.

    • Go
    • HTTP
    • Networking
    1

  • Vue 3 · 2026

    Flashflashy

    A full-stack flashcard app for building decks and studying them with spaced repetition.

    • Vue 3
    • Node.js
    • Express
    • MongoDB
    Flashflashy welcome screen with sign-in and register buttons

  • Python · 2025

    pdf-merger

    A tiny Flask app to upload, reorder and merge PDFs.

    • Python
    • Flask
    • JavaScript

Where I've worked

  1. Java Full-stack Engineer

    Now2024 — present

    Building and maintaining Java services and the web frontends that sit on top of them, from API design to deployment.

My toolbox

Languages

  • Java
  • Go
  • Python
  • JavaScript
  • TypeScript

Backend

  • Spring
  • Express
  • HAPI FHIR
  • REST
  • Server-Sent Events

Frontend

  • Vue 3
  • HTML & CSS

Data & infra

  • PostgreSQL
  • MongoDB
  • Docker
  • Cloudflare Workers
  • Vercel

Say hi

Find me on the platforms below — I'm happy to talk about projects, ideas or opportunities.

GitHub