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Dave Rzepa

Software engineer. Technical lead. Systems thinker.

I build reliable systems, help teams deliver, and make complex software easier to work on. My experience spans backend services, real-time networking, cloud infrastructure, developer tools, graphics, and engineering leadership. I’m bringing that breadth to contract projects across industries.

Global contract opportunities · San Cristóbal de las Casas, Mexico

david.rzepa@gmail.com · LinkedIn

Experience

Lead Programmer — Parallel

Jun 2024 – 2026

Lead programming on Parallel TCG, covering client and backend integration, mobile performance, delivery infrastructure and AI development tooling.

Projects: Parallel TCG

Made an application inspectable by AI agents. Built a Unity MCP server and driver that let an LLM play and inspect the application, alongside agent test scenarios, profiling, and a coverage ledger. Skills: MCP, AI agents, LLM integration, C#, Python, test automation, Unity. Transferable experience: Agent integrations, application instrumentation, and automated QA for complex interactive software.
Automated issue-to-review engineering workflows. Developed an autonomous bug-fixing workflow, deterministic issue triage, a PR readiness dashboard, and build-provenance checks connecting Jira, GitHub, and delivery pipelines. Skills: Jira, GitHub, CI/CD, developer experience, automation, AI agents, Python. Transferable experience: Internal developer platforms, engineering automation, and traceable delivery workflows.
Established reusable agent development practices. Created repository instructions, canonical agent skills, playbooks, and coordination around shared Unity resources. Skills: AI agents, documentation, developer experience, workflow design, resource coordination. Transferable experience: Introducing AI development tools with repeatable team practices and explicit coordination.
Built cloud observability with infrastructure as code. Built Grafana infrastructure on Google Kubernetes Engine using Terraform, with KPI dashboards and an analytics-breadcrumb prototype. Skills: Terraform, Grafana, GKE, Kubernetes, Google Cloud, observability, analytics. Transferable experience: Reproducible infrastructure, operational dashboards, and service visibility.
Owned build and release automation. Built and maintained GitHub-based build pipelines, platform build matrices, caching, versioning, and release delivery through Applivery and Steam. Skills: GitHub Actions, CI/CD, build engineering, release engineering, caching, Unity. Transferable experience: Repeatable releases, build performance, and multi-platform delivery.
Refactored authentication and backend integration. Worked on login architecture, Google Play Games and Steam authentication, token refresh, and API-client integration. Skills: authentication, token refresh, API integration, C#, backend services. Transferable experience: Identity flows, external service integration, and maintainable client/backend boundaries.
Improved network and serialization correctness. Refactored low-level netcode and worked on resynchronization, serialization, replay correctness, a serialization analyzer, and server tests in CI. Skills: networking, serialization, distributed systems, C#, static analysis, testing, CI/CD. Transferable experience: Debugging state consistency and building checks around difficult system invariants.
Adapted a desktop application for mobile. Optimized an existing PC game for mobile, including texture and GPU work, blur render textures, mobile rendering, and shaders. Skills: performance optimization, profiling, mobile, GPU, rendering, Unity, HLSL. Transferable experience: Resource-constrained applications, performance investigation, and cross-platform engineering.
Rebuilt and extended a complex client UI. Rebuilt the client UI, including collection and deckbuilder views, page architecture, card movement, draft-mode screens, and reward reveal flows. Skills: UI architecture, C#, Unity, refactoring, state management. Transferable experience: Complex application interfaces and restructuring established codebases.
Built AI simulation and evaluation tooling. Developed a headless match harness, heuristic AI, genetic deck evolution, cloud benchmarking, and server-side solo AI decks. Skills: simulation, heuristic AI, genetic algorithms, benchmarking, C#, cloud computing. Transferable experience: Automated evaluation, search and optimization, and reproducible simulation workloads.
Connected structured design data to LLM workflows. Worked on data for LLM-assisted card design, starter decks, and progression and unlock systems. Skills: LLM integration, data pipelines, C#, API integration. Transferable experience: Preparing application data for AI-assisted workflows and integrating generated output with product systems.

Principal Programmer — Offworld

Jan – Jun 2024

Engine modernization on Starship Troopers: Extermination, including Unreal Engine 5.4, Nanite, and World Partition.

Projects: Starship Troopers: Extermination

Modernized a production engine integration. Updated Starship Troopers to Unreal Engine 5.4, including Nanite and World Partition. Skills: Unreal Engine, C++, Nanite, World Partition, engine migration. Transferable experience: Upgrading complex production dependencies and adopting new platform capabilities.

Lead Programmer — PopReach

2021 – Aug 2023

Technical architecture, an eight-person programming team, backend integration, and live releases for PAYDAY: Crime War.

Projects: PAYDAY: Crime War

Hired and mentored eight programmers. Interviewed, hired, and mentored a team of eight programmers. Evaluated an inherited codebase and architected and estimated a rebuild for PAYDAY: Crime War. Skills: technical leadership, hiring, mentoring, architecture, estimation, code review. Transferable experience: Building engineering teams, evaluating legacy systems, and setting technical direction.
Established shared application foundations. Implemented dependency injection with VContainer, async/await state machines and API wrappers, a PlayFab configuration pipeline, a UniRx UI system, and an Addressables pipeline, then trained the team in their use. Skills: C#, dependency injection, async/await, reactive programming, architecture, configuration management, Unity. Transferable experience: Modular application architecture, asynchronous systems, and enabling teams through shared foundations.
Integrated managed backend services. Integrated PlayFab authentication, remote configuration, player data and inventory, matchmaking, and multiplayer servers. Skills: PlayFab, authentication, backend services, data storage, configuration management, API integration, C#. Transferable experience: Managed service integration, identity, remote configuration, and persistent user data.
Built serverless functions and user-data migrations. Used Azure Functions with a shared DLL between client and server, robust user-data migrations, and queue-backed leaderboard prize granting using Azure Queue Storage. Skills: Azure, Azure Functions, C#, serverless, data migration, queues, distributed systems. Transferable experience: Serverless backend development, shared contracts, durable asynchronous work, and evolving stored data.
Integrated real-time communication. Integrated Photon Fusion for real-time networking and Photon Chat for messaging. Skills: real-time systems, networking, Photon Fusion, messaging, C#. Transferable experience: Real-time client applications and communication-service integration.
Supported live delivery and operational visibility. Deployed eight feature releases and three hotfixes. Added New Relic logging, dashboards, and alerting, and helped the analytics team with KQL queries and technical graphs. Skills: release engineering, New Relic, observability, KQL, analytics, incident investigation. Transferable experience: Operating live software, release coordination, and turning telemetry into useful engineering information.
Built continuous deployment across clients and backend environments. Implemented Jenkinsfile-based continuous deployment with AWS build agents, Google Play and TestFlight publishing, and a .NET tool for deploying branches and pull requests to PlayFab environments. Included Slack integration, restartable stages and deployment guards. Skills: CI/CD, Jenkins, AWS, C#, .NET, PlayFab, TestFlight, Google Play, release engineering. Transferable experience: Repeatable releases, ephemeral review environments, and guarded deployment automation.

Senior Programmer — Bossa Studios

2018 – 2021

Distributed simulation, data-oriented systems, graphics, physics, and AI across Worlds Adrift, I Am Fish, Surgeon Simulator 2, and Hogwash. Also worked on an unnamed Python/data-science project documented in archived CVs.

Projects: I Am Fish, Surgeon Simulator 2, Hogwash, Worlds Adrift, Bossa data-science project (name not documented)

Built a data-oriented entity system. Developed a pure C# entity-component system for Worlds Adrift, usable inside and outside Unity, with bitwise entity filtering and T4-generated components and marshaling to synchronize SpatialOS and ECS data. The 2019 CV details batch component changes, JSON entity blueprints with multiple inheritance, throttle masks for amortizing system work, Zenject dependency injection, and unit tests around core routines. Skills: C#, data-oriented design, ECS, code generation, distributed systems, SpatialOS, performance optimization. Transferable experience: High-performance data processing, generated contracts, and decoupling core systems from frameworks.
Solved latency and distributed simulation handovers. Implemented spline-based extrapolated ship movement for latency compensation and handover between physics servers, NTP time synchronization, and diagnostic graphing in Worlds Adrift. Skills: distributed systems, networking, time synchronization, NTP, latency, C#, simulation. Transferable experience: Time-sensitive distributed applications, state handover, and diagnosing synchronization problems.
Extended asynchronous cloud persistence. Modified Scala server code to save and load ship-blueprint XML through AWS, making extensive use of futures and promises. Skills: Scala, AWS, asynchronous programming, XML, backend services, data storage. Transferable experience: Server-side service development, cloud persistence, and asynchronous I/O.
Implemented custom GPU rendering and parallel physics. Built custom Unity HDRP effects for I Am Fish: underwater scattering and absorption with compute shaders and signed distance fields, water normals, caustics, reflections, procedural glass caustics, and a jobified buoyancy simulation. Skills: HLSL, compute shaders, GPU, rendering, physics, parallel programming, Unity, mathematics. Transferable experience: GPU computing, numerical simulation, parallel execution, and graphics engineering.
Built custom visibility and performance systems. Developed custom occlusion culling for Surgeon Simulator 2 with jobified runtime baking and compute-shader portal visibility, and optimized and debugged custom netcode. Archived CVs also list UI and HTTP networking work on Surgeon Simulator 2. Skills: compute shaders, HLSL, parallel programming, performance optimization, networking, Unity. Transferable experience: Profiling and optimizing complex real-time software with CPU and GPU workloads.
Tuned autonomous behavior and control systems. Originated Hogwash during a game jam and developed and tuned behavior-tree heuristics, a PID controller for path following, and ORCA dynamic avoidance. Skills: heuristic AI, behavior trees, PID controllers, control systems, simulation, mathematics, C#. Transferable experience: Autonomous agents, feedback control, navigation, and heuristic decision systems.
Led a server-side SDK and architecture migration. The 2019 CV describes spearheading the Worlds Adrift migration of server-side logic from the SpatialOS Scala SDK to the C# SDK, including a bespoke data-oriented ECS and generated synchronization systems. Skills: C#, Scala, SpatialOS, distributed systems, code generation, software architecture, migration. Transferable experience: Modernizing a distributed production system while redesigning core abstractions and integration boundaries.
Reduced vector serialization size in a distributed simulation. Implemented a new Vector3 serialization schema for Worlds Adrift, reducing the representation from 192 bits to 96 bits per entity; the archived CV reports that often only 64 bits changed. This is a representation-level improvement, not a claim of overall network bandwidth reduction. Skills: serialization, networking, C#, bitwise operations, performance optimization. Transferable experience: Compact data formats and precise optimization of high-frequency distributed state.
Validated an ECS across client and server. Rewrote Worlds Adrift’s Blight feature using the ECS on both client and server, exposing and filling gaps in the framework API and demonstrating its use for a substantial production feature. Skills: C#, ECS, API design, client-server systems, refactoring. Transferable experience: Validating foundational architecture through a real feature and improving interfaces from implementation feedback.
Delivered the final Worlds Adrift update with its community. As the last developer on the Worlds Adrift team, designed and implemented its final update in collaboration with the community, including the end-of-world events. Skills: delivery, community collaboration, product design, C#, live operations. Transferable experience: Owning delivery through a product transition and working directly with users on the final experience.
Worked on Python web services and data science. An archived Bossa project lists Django, Celery, natural language processing, deep learning and statistical analysis. The 2019 CV describes learning Django and researching data-science and machine-learning techniques. The records do not establish model architectures, dataset sizes, production scale, or quantified outcomes. Skills: Python, Django, Celery, NLP, deep learning, statistical analysis, machine learning. Transferable experience: Python service development and research-oriented data science, with the documented scope kept distinct from later LLM agent engineering.

Lead Programmer — Ubisoft London

2014 – 2018

Led a three-person programming team and maintained and extended Hungry Shark Evolution. Built prototypes in the Future Games of London incubation programme.

Projects: Hungry Shark Evolution, Future Games of London incubation prototypes

Led delivery on a long-running mobile product. Managed an internal team of three programmers on Hungry Shark Evolution, maintained an established codebase, and delivered gameplay features, optimizations, and bug fixes. Skills: technical leadership, team management, mobile, maintenance, performance optimization, delivery. Transferable experience: Leading a small engineering team and sustaining a mature software product.
Built a rapid-prototyping framework and six prototypes in twelve weeks. At Future Games of London (Ubisoft), built a framework for rapid prototyping and six distinct prototypes in twelve weeks. Developed a fuller gameplay and frontend prototype and an online multiplayer prototype using deterministic lockstep with Photon TrueSync. Skills: prototyping, framework design, Unity, C#, networking, deterministic lockstep, Photon TrueSync. Transferable experience: Rapid technical validation, reusable foundations, and deterministic network simulation.
Integrated cloud features and live operations on a mobile product. Implemented cloud-save frontend, remote JSON configuration and Amazon Insights A/B testing, analytics, error logging with LogEntries, customer-support integrations, and GameSparks live-event client, backend logic and dashboards. Later replaced GameSparks live events with an in-house backend and built workflow tools for reviewing remote configuration changes. Skills: backend services, remote configuration, A/B testing, analytics, observability, API integration, GameSparks, mobile, tooling. Transferable experience: Service integration, operational visibility, safe remote configuration, and replacing third-party dependencies.

Unity programmer, game designer and Head of Games — UNIT9

2010–2014 (documented projects; Head of Games in 2014)

Unity engineering and product design across six documented projects, progressing to Head of Games; strategy, proposal prototyping, UX, analytics, and reusable engineering frameworks. The year range describes documented projects rather than exact employment dates.

Projects: Decromancer, Electric Tentacle, Domino’s Pizza Hero, Nano Panda, Xtreme Xrunch Kart, W.A.R.P.

Head of Games: strategy, proposals and hiring (2014). Performed market research and developed business strategies. Served as technical and game-design consultant and prototyper on business proposals, and interviewed applicants for multiple roles. Skills: technical leadership, market research, business strategy, prototyping, hiring, technical consulting. Transferable experience: Connecting technical feasibility, product direction, commercial proposals, and recruitment.
Creative direction and lead engineering on Decromancer (2013). Creative Director and Lead Unity programmer: game design, UX, narrative and copywriting, art direction and marketing, alongside C# engineering using NGUI and Flurry Analytics for iOS and Android. Worked closely with an illustrator, provided creative briefs and feedback, and developed narrative and gameplay direction. Skills: Unity, C#, NGUI, Flurry Analytics, iOS, Android, UX, creative direction, product design. Transferable experience: Owning both implementation and product direction, communicating across design and engineering.
Procedural systems and lead development on Electric Tentacle (2012). Lead Unity programmer and lead game designer. Built modular infinite-level generation using Perlin noise, allowing zone-specific changes without code edits, plus object pooling for performance. Used C#, SpriteManager2 and Flurry Analytics for iOS and Android, and designed gameplay and UX. Skills: Unity, C#, procedural generation, Perlin noise, object pooling, iOS, Android, UX, performance optimization. Transferable experience: Reusable generation systems, configurable content, and allocation-conscious application engineering.
Procedural geometry and scoring for Domino’s Pizza Hero (2011). Lead Unity programmer. Developed real-time mesh and texture deformation and mesh relaxation algorithms, analyzed dough shape to score evenness, and generated simplified mesh colliders for topping physics. Integrated native plugins and Google Analytics, and built UI view and transition systems. Skills: Unity, C#, procedural geometry, mesh deformation, physics, algorithms, native plugins, Google Analytics, UI architecture. Transferable experience: Interactive simulation, geometric algorithms, native integration, and measurable product experiences.
Programming, gameplay and level design for Nano Panda (2011). Documented as solo programmer in the 2012 CV and lead Unity programmer in the 2014 CV. Implemented the project in C# with EZGUI and SpriteManager2, and contributed gameplay and level design. Skills: Unity, C#, EZGUI, SpriteManager2, gameplay design, level design. Transferable experience: Delivering an interactive product across programming and design responsibilities.
Unity development and game design for Xtreme Xrunch Kart (2010). Unity programmer and game designer, contributing C# implementation, Unity GUI, gameplay design and level design. Skills: Unity, C#, UI, gameplay design, level design. Transferable experience: Building complete interactive experiences and collaborating across implementation and design.
Programming, game design and sound design for W.A.R.P. (2010). The 2012 CV records programming, game design and sound design responsibilities on W.A.R.P. at UNIT9. Skills: Unity, programming, gameplay design, sound design. Transferable experience: Combining engineering, interaction design, and audio implementation in a shipped project.
Built reusable architecture and interface frameworks. Developed internal Unity frameworks, UML diagrams and technical specifications, including interfaces between Unity and layers built by other teams. Built custom view and transition sequencing frameworks used in Domino’s Pizza Hero and Electric Tentacle, plus procedural Bézier and B-spline track generation. Skills: software architecture, UML, technical specifications, API design, UI architecture, C#, splines, framework design. Transferable experience: Reusable application frameworks, clear subsystem boundaries, technical design, and animation sequencing.
Combined analytics, UX and rapid prototyping. Selected analytics events and analyzed results across several games using Flurry and Google Analytics. Designed UX wireframes, iterated on feedback loops and balancing, and developed numerous prototypes at UNIT9. The archived CV discusses retention, conversion, acquisition cost and revenue metrics as product-design considerations. Skills: analytics, Flurry Analytics, Google Analytics, UX, wireframing, prototyping, product design. Transferable experience: Turning user behavior and product requirements into testable prototypes and informed design decisions.

Open-source and personal software engineering — Independent projects

Selected projects

ZzzOps agentic engineering workflow, HyperTween Unity ECS framework, and earlier simulation and tooling experiments. Also conceived and directed the AI-assisted development of this multilingual career assistant.

Projects: ZzzOps, HyperTween, Void Exiles, Ask me about Dave Rzepa — AI career assistant

Created ZzzOps, an open-source agentic engineering workflow. ZzzOps turns project policy, specifications, tasks and dependencies into a durable goal graph backed by GitHub Issues, and provides autonomous coding agents with verification, blocker handling and resumable execution. Its Python-based implementation supports Codex and Claude Code plugins and is published under Apache-2.0. Dave identifies it as his open-source work. Skills: AI agents, agentic engineering, Python, GitHub API, developer tooling, workflow design, verification, open source. Transferable experience: Engineering the orchestration, durable state, feedback loops and operating boundaries around autonomous coding agents.
Created HyperTween, a Unity ECS tweening framework. HyperTween is an MIT-licensed C# tweening framework built on Unity ECS, designed for high-performance transform updates, a fluent API, extensible outputs, complex sequencing, accurate timing, conflict detection and compatibility with managed Unity components. Dave describes its development as almost entirely traditional hands-on coding. Skills: Unity ECS, C#, data-oriented design, Burst, Unity Job System, performance optimization, API design, animation, open source. Transferable experience: Data-oriented library design, efficient parallel workloads, precise sequencing, and accessible APIs over performance-focused internals.
Explored simulation, numerical optimization and programmable UI. A personal project, Void Exiles, documented in the 2019 CV used Unity NetCode and HDRP, dynamically sized matrix and vector classes for bounded-variable least-squares thruster allocation, a hybrid GameObject view layer, XML-based customizable UI binding, and runtime C# compilation for player control macros. Its listing under a combined Bossa/personal heading does not establish a commercial release or employer ownership. Skills: C#, Unity ECS, NetCode, HDRP, least squares, numerical optimization, simulation, XML, runtime compilation. Transferable experience: Numerical methods, programmable software, data-oriented simulation, and user-configurable interfaces.
Directed AI-assisted development of a multilingual recruiter assistant. Conceived and directed this career site through collaboration with Codex, from the semantic career-record concept to the minimal conversation interface. The Node.js/Express service uses Gemini through Vertex AI to answer recruiter questions and compare uploaded job descriptions against source-backed contributions, with separate system instructions, untrusted-input boundaries, structured outputs and validated citation IDs. Related project videos load automatically to thumbnails; PDF exports are assembled from selected records rather than generated claims. Deployment uses Google Cloud Run and service-account OAuth instead of a browser API key. Local IP-to-country lookup selects a default language; UI translations are generated on demand and cached by language and UI version in private Cloud Storage. Questions, answers, citations and documented gaps are retained privately for 90 days for service improvement; original files and full job descriptions are retained only by explicit opt-in. Append-only analytics storage is retrievable through authenticated owner tooling rather than a public dashboard. Document text is extracted by a separate IAM-protected Cloud Run service with its own unprivileged identity and bounded parsing. A shared atomic daily request budget persists across web-service restarts. Dave guided design iterations, factual corrections and feature priorities while Codex assisted implementation and verification. Skills: AI engineering, LLM integration, Gemini, Vertex AI, Node.js, Express, Google Cloud Run, OAuth, structured outputs, PDF generation, internationalization, Google Cloud Storage, semantic data, privacy, Codex. Transferable experience: Designing and delivering an AI application around grounded evidence, explicit trust boundaries, multilingual UX and cloud deployment.

Projects

Parallel TCG

Associated roles: Parallel

Project context: Parallel TCG is a science-fiction digital trading-card game from Parallel Studios. Players choose among five factions, build decks, and compete in strategic card battles, using units, abilities and banked cards to build combinations.