Freelance Principal Software Engineer – Platform Architecture and Developer Enablement (Hands-O[...]

Overview Project Duration: 6-12 months, extension possible Commitment: Full-time Job Description Our client is looking for a hands-on Principal Software Developer with deep computer science fundamentals and a pragmatic, product-oriented mindset. You combine strong architectural thinking with the ability to ship high-quality code thoughtfully and predictably. You are fluent in modern engineering practices, comfortable in heterogeneous, service-oriented and distributed environments, and focus on writing robust, maintainable code for systems that scale. You will help evolve a business-critical platform—leading the transition from a heterogeneous semi-distributed codebase to a strategically aligned, reliable, and scalable architecture. You will balance delivery speed with long-term sustainability and champion tools and techniques that multiply engineering effectiveness.

What you\'ll do Design, build, and run a business-critical software platform using modern frameworks and programming languages Spearhead the migration from a semi-distributed codebase to a unified, scalable architecture Analyze trade-offs, risks, dependencies, and user value to drive technical decisions Solve complex technical problems hands-on, not from the sidelines Operate close to production: build it, ship it, support it Champion clean code, test coverage, and performance-first thinking Evaluate and apply emerging developer tools where they provide real leverage (e.g., GitHub Copilot, GPT agents, etc.) Who we\'re looking for 8 to 12 years of professional experience in software development with at least 80–100% of your last 2-3 years spent coding, shipping, and deploying Expert knowledge of C#/.NET Core Proven track record of delivering production-grade systems Proficient in

functional programming and strong static typing (F#, Scala 3, Rust, Haskell, Kotlin, OCaml, etc.) Applied architectural knowledge: modular monoliths, microservices, event-driven systems, actors, etc. Confident working with relational databases (schema design, migrations, tuning) Familiarity with modern delivery stacks: Git, GitOps, CI/CD, Docker, etc. Strong communication and collaboration skills; self-starter attitude Fluent English (C1/C2); German is a strong plus Nice to Have Experience with Kubernetes and Infrastructure-as-Code tools (e.g. Terraform, Pulumi) Familiarity with AI-assisted engineering tools (Copilot, GPT, linters, analyzers) Experience with platform abstraction, developer enablement, or internal tooling