Freelance Principal Software Engineer – Platform Architecture and Developer Enablement (Hands-On Coding / Modern Stack)

Location: European Union - Remote

Project Duration: 6-12 months, extension possible

Commitment: Full-time

Languages: English, German is a plus

Please read before applying:

This role is for principal developers who are still in the code 80% of their time, solving real problems, deploying real systems, and continuously pushing quality forward. We need to solve problems in a pragmatic, code-focused way. If your recent roles were mostly management, team leadership, or coordination, this is likely not the right fit.

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.

- Experience working in distributed systems: idempotency, consistency, backpressure, observability

- 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