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Juozas Žilys
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Juozas Žilys

Senior full-stack engineer on enterprise systems — .NET, React, and whatever the problem asks for.

Vilnius, Lithuania · juozaszilys@hotmail.com

Experience

  1. Senior Full-Stack Engineer · DAVIVA

    Vilnius, Lithuania

    May 2021 – present

    • Build and modernize a .NET 10 / React enterprise ERP for the automotive aftermarket (parts inventory, orders, invoicing, shipping, multi-marketplace sync) — 780+ merged PRs since 2021, roughly a third of the platform's entire PR history.
    • Own features end-to-end across the .NET backend, React frontend, MariaDB, Elasticsearch, Hangfire, and SignalR real-time hubs. Drove the solution-wide migration to .NET 10, including Docker image and CI workflow optimization.
    • Author the codebase's custom Roslyn analyzer suite and incremental source generators — propose the rules, write the analyzers, own enforcement in CI. The suite scales code-quality enforcement beyond me: repeated mistakes that review alone wasn't catching become compile-time errors instead of recurring PR comments.
    • Drive the DDD refactor of the Product domain (aggregate roots, domain events, value objects, result pattern) and the platform-wide database services rewrite onto Dapper.
    • Rewrote the invoice system to introduce a full edit-history audit trail, and own the PDF-generation pipelines (invoices, shipping labels, picking lists, QR stickers, financial reports).
    • Built the warehouse hardware integration surface — ParcelCube measurement & weighing, custom multi-protocol scale drivers with automatic place/remove detection, a context-aware QR scanner that resolves a dozen ways depending on workflow, and the courier label printing pipeline.
    • Authored the platform's direct-to-database PrestaShop integration library — bypasses the slow / unreliable official API for fast product CRUD, reads order state from the DB directly, and verifies payment by calling the payment provider instead of trusting PrestaShop's payment flag.
    • Built the marketplace pricing-intelligence scrapers used for same-product lookups before listing decisions, with per-marketplace adapters and tolerant parsing.
    • Integrate marketplaces (eBay, Allegro, Amazon SP-API, Autoplius, Autogidas, RRR, DalysLT, Daviva/PrestaShop), payment gateways (Opay, Paysera), shipping carriers, and Google Gemini vision for part recognition.
    • Custom modules, faceted-search caching, MySQL triggers, and direct interventions in PrestaShop's core search logic — the catalog page went from ~60s loads with 200k products to under 1s on the same hardware.
    • Helped migrate the platform's authorization from ASP.NET's built-in auth onto Keycloak — central identity, proper token issuance / refresh / expiration, less homegrown plumbing.
    • Help run the platform's running infrastructure: Docker, Cloudflare (incl. firewall rules), nginx, DigitalOcean droplets, Ubuntu server administration, CI/CD, VPN and SSH tunnel access for the team, and security & load testing of our own surface.

  2. Depot Clerk · DPD

    Dartford, United Kingdom

    Dec 2020 – Mar 2021

    • Monitored driver activity and parcel-flow compliance in DPD's logistics system.
    • Handled data entry and coordination with depot staff to keep routes on schedule.

  3. Node.js Developer — Internship · Indie development team (remote)

    Canada (remote)

    Jan 2020 – May 2020

    • Built and maintained features on a Discord bot using Node.js and the Discord API.
    • Worked with the team on debugging and shipping improvements across time zones.

  4. Web Developer — Internship · Logistics company (Lithuania)

    Vilnius, Lithuania

    Jan 2019 – May 2019

    • Built a complete logistics company website end-to-end — PHP / PostgreSQL backend, jQuery / JavaScript / CSS frontend.
    • Designed the database, implemented the UI, shipped solo.

Skills

Languages & runtimes
C# / .NET 10, TypeScript, JavaScript, PHP, Python, Rust, C, Java, Kotlin, Bash, SQL
Frontend
React, Astro, Vite, Tailwind, Material-UI, HTML5 / CSS3, SignalR client
Backend
ASP.NET Core, Entity Framework Core, Dapper, SignalR, Hangfire, Elasticsearch (NEST), RabbitMQ, MediatR
Data
MySQL / MariaDB, PostgreSQL, Elasticsearch, schema design, query optimization, caching strategies
Architecture & patterns
Domain-Driven Design, Clean Architecture, CQRS, Result pattern, event-driven systems, repository / unit-of-work
Tooling & compiler work
Custom Roslyn analyzers, incremental source generators, code fix providers, EditorConfig
Systems & desktop
Rust, Tauri 2, WebAssembly (C → Emscripten), PyQt6, WPF, WinForms, Electron
Mobile
Native Android (Kotlin, Java, Android Studio). Prefer cross-platform via Electron, MonoGame, or web targets when reach matters more than native polish — covers Android, iOS, desktop, and consoles from one codebase.
Game engines
Unity (C#, indie multiplayer; published Euphelia libraries on NuGet), Unreal, Godot, MonoGame, plus custom C++ engine work (DirectX, native binary patching from the Luna Online modernization). Pick the engine by project, not by habit.
Cloud & hosting
Provider-agnostic — pick by workload and budget. AWS (Lambda, S3, cost safeguards & monitoring), DigitalOcean (droplets, App Platform, GPU instances), Hostinger (VPS game servers — PaperMC + custom website — and WordPress sites when that's what the job calls for), bare Ubuntu anywhere
Infra & DevOps
Docker, GitHub Actions, Ubuntu server administration, nginx, Cloudflare, Kubernetes client, OpenTelemetry, CI/CD pipelines
Security & access
Penetration testing and hardening of own infrastructure, Cloudflare firewall rules, VPN and SSH tunnel access management for team, identity / auth migrations (Keycloak, OAuth2 / OIDC)
AI / LLM
Google Gemini (vision), Claude API, multi-agent orchestration, prompt engineering, streaming / structured outputs
Reverse engineering
.NET decompilation and inspection (ILSpy, dnSpy, dotPeek-class tooling), native-binary reverse-engineering on compiled game clients for patching and source recovery — practiced primarily on a long-running modernization of a shuttered C++ MMORPG
Multimedia
Adobe Premiere Pro, Sony Vegas, Adobe Photoshop, After Effects, Autodesk Maya, ZBrush, pixel art, Strudel (live-coding music)
Methods
Agile / Scrum, Git, API design, test-driven development

Education

  1. SMK University of Applied Social Sciences

    Professional Bachelor of Informatics Sciences in Software Engineering

    2017 – 2020

  2. Vilnius, Senvage Gymnasium

    Secondary Education

    2013 – 2017

  3. Vilnius, Balys Dvarionas Ten-Year Music School

    Music Education

    2004 – 2013

Certificates

  • Japanese for advanced — Dalia Dokšaitė, 2016 (40h)
  • Japanese for beginners — Dalia Dokšaitė, 2015 (40h)

Languages

  • Lithuanian — Native
  • Russian — Fluent
  • English — Fluent
  • Japanese — Beginner (formal courses, certificate 2016)
  • Polish — Basic