Janne Keipert

A self-hosted game server management platform that makes it simple and beautiful to deploy, manage, and monitor game servers on your own hardware. Cosy provides a modern web UI for full container lifecycle management, real-time metrics and logs, file browsing, user and quota management, RCON integration, and event-driven webhooks. Servers are created from a curated template library and run as Docker containers, with support for both Docker Compose and Kubernetes deployments. We also created a dedicated Minecraft Fabric mod which collects in-game metrics like TPS and player count and pushes them back to the platform.

A subdomain management service for the cosy-hosting.net platform. Users register an account, claim subdomains (e.g. castle.play.cosy-hosting.net), and point them at their own Cosy instance IP — the backend automatically provisions and updates the corresponding AWS Route53 A records. A Cosy+ billing tier (via Stripe) unlocks custom label choice, CNAME support, and higher quotas. The backend is a Spring Boot 4 / Java 21 REST API with JWT auth, rate limiting, and a Prometheus metrics endpoint. The frontend is a React 19 SPA with full i18n (EN/DE), TOTP two-factor authentication, Cloudflare Turnstile bot protection, and QR code setup for 2FA. Both services are containerized, deployed to Kubernetes via Kustomize and ArgoCD, and covered by a Playwright end-to-end test suite.

A mobile app (React Native/Expo) for discovering and tracking Die drei ??? audiobook albums. It randomly suggests an unseen album from the full catalog, lets you open it directly on Spotify, Apple Music, or Deezer, and tracks your listening history. A history screen shows your overall progress across the entire series with filtering by narrator, album type, and other criteria. Album details include descriptions, narrator characters, ratings, and release dates. Push notifications alert you when new albums are released.

Blockworks is an AI build-benchmark showcase for Minecraft. Different large language models receive the same building prompt through a Minecraft MCP server, and their creations are captured and compared side by side. The web app groups builds into benchmark tests (e.g. a cosy house), lets you filter by model and effort level, and renders every build as an interactive 3D voxel scene in the browser. Builds are captured from a live Minecraft world, exported as palette-indexed voxel data, and served through a containerized app deployed on Kubernetes with ArgoCD.

A full-stack web app that connects to a user's Steam library and displays their games with high-quality custom cover artwork from SteamGridDB. Users enter their Steam profile URL to load their game collection - including Family Shared titles - and can browse alternate, static, and animated cover styles for each game. The backend reactively fetches and caches cover metadata, while the frontend provides a responsive browsing experience with smooth animations.

A community-driven web platform for discovering, creating, and sharing ability lineups for the tactical shooter Valorant. Players can browse lineups filtered by map, agent, and ability, visualized on interactive canvas-based maps showing stand and landing positions. Authenticated users can create their own lineups with screenshot uploads, organize them into guides, and share them with the community.

A full-stack web application for administering and tracking athlete performances for the Deutsche Sportabzeichen (German Sports Badge). Trainers can register athletes, record performances across disciplines like endurance, strength, speed, and coordination, and track medal eligibility based on age- and gender-specific thresholds. Athletes can view their own progress, certificate status, and medal history. The platform features role-based access control, real-time updates via WebSocket, and multi-language support.

A mail service which allows the users to configure SMTP connections and then use an API to send mails through those connections. Mails are being kept in storage for 30 days for monitoring and then deleted from storage.

The school finals project of my computer science course. A 2D side-scrolling action platformer Metroidvania game built in our own 2D Game Engine completely from scratch using JavaX Swing. The player traverses a tile-based world with physics-driven movement including running, jumping, wall-jumping, and dashing. Enemies, liquids, coins, fireballs, and interactive event areas populate the world, which is loaded from JSON map data. The game features a skill tree with upgrades, a minimap, HUD with health display, sprite animations, a camera system, and background music. A companion website built with Vue.js serves as a landing page and tutorial hub.

A price-tracking and notification service for Star Citizen ships. The app monitors the Roberts Space Industries pledge store for pricing changes and sends email notifications when ships within a user's configured price range go on sale or get discounted. Users can register, set minimum and maximum price thresholds, and receive hourly updates via email.

A cloud-native student management portal built as a microservices and micro-frontend architecture in a university agile software engineering course. Multiple teams each develop independent domain services - including room booking, timetable management, document management, examination grading, notifications, parking analytics, and more - all composed into a unified single-spa frontend. The system uses Keycloak for centralized authentication, MinIO for file storage, and is fully containerized for Kubernetes deployment.

A browser-based visual editor for designing and documenting software architecture diagrams. Users can build diagrams from a library of 60+ pre-built component types across categories like frontend, backend, datastores, DevOps, and messaging, and connect them with protocol-specific edges such as REST, WebSocket, gRPC, or GraphQL. Diagrams can be exported as images or shared as JSON files. All data is stored locally in the browser - no backend required.

A distributed event-driven message publishing and subscription platform. Users create projects with topics that other projects can subscribe to. When a message is published to a topic, it is automatically delivered to all approved subscribers via HTTP webhooks with retry logic and exponential backoff. The system features multi-tenant project isolation, fine-grained role-based access control, and full HTTP exchange logging for debugging delivery issues.

A multi-tenant, in-cluster Kubernetes database browser. Strata runs inside a Kubernetes cluster, automatically discovers the databases running in that cluster, and lets authenticated users browse and query the ones they've been granted access to — without kubeconfig files, manual connection strings, or port-forwarding. It supports PostgreSQL, MySQL, MongoDB, Redis, InfluxDB, and Loki. Features include role-based access control with namespace- and database-level grants, a global safe-mode for production namespaces, audit logging, user management, drag-and-drop grouping of datasources, and a full GitOps deployment model via ArgoCD.