Software Engineer & Founder

Building high-performance applications and taking products from concept to launch. Passionate about solving hard technical problems and shipping software that people rely on every day.

William Olsson, Software Engineer & Founder based in Stockholm, Sweden

Focus Areas

Full-Stack Development

  • Modern web applications
  • API design & integration
  • Database design & management
  • Code profiling & optimization
  • Agentic development workflows

Systems & Performance

  • High-throughput backend services
  • Distributed systems architecture
  • Reverse engineering & instrumentation
  • Low-level performance tuning

Product Leadership

  • End-to-end product ownership
  • Licensing & authentication systems
  • Release automation & delivery
  • User feedback-driven roadmaps

Additional Competencies

Performance Engineering

Services handling millions of requests per month, memory and CPU profiling, and optimization of hot paths in both managed and native code

Security & Authentication

OAuth/OIDC integration, custom licensing systems, and secured client-server communication for commercial desktop products

Client & User Experience

Direct engagement with users and third-party developers, feedback integration, and tooling that lets non-developers build without code

DevOps & Observability

Docker containerization, Jenkins CI/CD pipelines, and Prometheus/Grafana monitoring for automated, zero-touch releases

Projects

Celestial Rift logo

Celestial Rift· Pixel-art roguelike

A pixel-art bullet heaven for PC where a cosmic casino sends its monsters through the Rift. Survive the horde, stack ridiculous builds, gamble at honest(ish) odds and take on the House itself. Upcoming on Steam.

  • 28 evolving weapons, 20 runes and 66 stacking items
  • 16 heroes, each with a signature trick
  • Six dimensions with their own weather, events and music
  • Five headline bosses and a final fight against the House
  • Double or Nothing, slot machines and rift roulette
C#UnityURPPythonNumPyFFmpeg
EternalClient logo

EternalClient· MMO automation client

A high-performance automation client for a popular MMO with an extensive script API, unlimited instances, packet and injection interaction modes, a low CPU/memory footprint and remote monitoring.

  • Extensive script API for fast bot development
  • Unlimited concurrent instances per machine
  • Packet and injection interaction modes
  • Cross-platform: Windows, Linux and macOS
  • Remote monitoring & CLI launchable
JavaTypeScriptNext.jsPostgreSQLDocker
HoltWalker logo

HoltWalker· MMO pathfinding API

A high-performance pathfinding API for a popular MMO. Resolves optimal routes across every zone and level, honoring quest, skill and item requirements as it walks.

  • Requirement-aware routing (quests, skills, items)
  • 12,000+ transport links: doors, teleports, shortcuts
  • Full coverage of 327M tiles across the game world
  • Bank locator with top-5 ranked results
  • Wilderness avoidance & batch REST queries
GoRedisDockerPrometheusGrafana

Professional Experience

  1. Doubleflow

    Software Developer · Stockholm

    Sep 2021 – Sep 2026

    Intern Sep–Nov 2021, then full-time

    • Led the rebuild of the company's web platform onto a modern ASP.NET Core stack, driving the migration to FastEndpoints and newer .NET versions
    • Rebuilt the legacy game-building system into a visual scripting tool in Blazor, letting non-developers create interactive games, quizzes and training experiences without writing code
    • Built the client-side system that renders and plays those experiences back to users in real time
    • Built operator tooling for customer onboarding, role-based permissions and usage reporting
    C#ASP.NET CoreBlazorFastEndpointsSQL

Independent Ventures

  1. Celestial Rift

    Solo Game Developer · Indie

    Mar 2026 – Present

    Upcoming on Steam

    • Designing, building and marketing a pixel-art action roguelike for PC in Unity and C# as the sole developer
    • Built 28 weapons with evolutions, 20 runes, 66 items, 16 heroes, 36 monsters, 6 boss fights and a raid across 6 dimensions
    • Kept hundreds of enemies on screen at once with pooled, struct-based projectile and VFX systems
    • Built a synthesizer and composition engine in Python behind every sound effect and the full soundtrack
    • Built a headless test harness where a bot plays full runs, and a balance benchmark that measures every weapon across parallel headless builds
    • Produced the trailer and Steam store art from scripted 60 fps gameplay capture, with original music made on the game's own synthesizer and every shot timed to the beat
    C#UnityURPPythonNumPyFFmpeg
  2. EternalClient

    Founder & Software Engineer · Self-employed

    Mar 2023 – Apr 2026

    • Founded and shipped a cross-platform desktop application for Windows, Linux and macOS
    • Built the web platform and marketplace in TypeScript, React and Next.js, where third-party developers listed and sold their work
    • Designed a high-performance pathfinding service serving up to 13 million requests per month
    • Built the licensing and authentication system securing communication between client and server
    • Automated build, testing and release so updates reached users without manual installs
    JavaTypeScriptReactNext.jsGoDocker
  3. LostClient

    Founder · Self-employed

    Dec 2019 – Oct 2023

    • Built and ran an automation platform for a large online game, giving players a scripting API to build their own tools
    • Grew it to over 3 million sessions and roughly 20 million hours of runtime
    • Built the licensing, authentication and usage analytics behind it, shaping the roadmap from community feedback
    JavaMySQLRedis

Beyond Code

When I'm not building software, you'll find me out on a trail, behind a drum kit, or taking something apart to see how it works. Curiosity about what happens under the hood is what got me into engineering, and it still shapes how I approach every problem.

Hiking
Drumming
Side Projects
Reverse Engineering
Learning

At a Glance

Based in
Stockholm, Sweden
Languages
Swedish (native), English (fluent)
Background
Self-taught, five years of professional .NET development
GitHub
@LostVirt

Let's Connect

Looking for new opportunities in full-stack and backend engineering, technical ownership, or founding roles. Particularly interested in performance-critical systems, developer tooling, and products with real users at scale.

Email
contact@wolsson.dev
Location
Stockholm, Sweden / Remote
GitHub
github.com/LostVirt