Senior Backend Software Engineer

Freelance Senior Backend Software Developer (Contract)

Location: Poland, remote based in Poland

Salary: Up to 40 EUR per hour

Length: An initial 3 months, with likely extensions

We’re looking for an experienced Senior Backend Software Developer to join a high-impact API Platform Team on a freelance contract basis.

About the Role

Our client's team manages the “front door” of digital services, their API management platform, playing a critical role in shaping the customer experience. They focus on improving platform quality, scalability, and enabling self-service capabilities for internal engineering teams through robust system engineering and software development.

This is an exciting opportunity to contribute to key ongoing initiatives within a modern, cloud-based platform environment.

What You’ll Be Doing

• You’ll collaborate closely with a cross-functional team to deliver impactful backend solutions that enhance platform performance, reliability, and developer experience. Depending on your expertise, you will:
• Design and build core features for a monetization service, supporting real-time transactions and balance computations
• Improve infrastructure to reduce operational overhead and strengthen security
• Develop backend APIs and abstraction layers to enable seamless system integrations
• Contribute to internal developer tooling, including extending platform capabilities and usability

What We’re Looking For

• Strong hands-on experience with Golang
• Solid understanding of PostgreSQL, including sharding, partitioning, and handling write-heavy workloads
• Proven experience building REST and gRPC APIs
• Commitment to high-quality code, including testing best practices
• Experience with CI/CD pipelines, GitHub, and modern development workflows
• Familiarity with GitOps, infrastructure as code, and automation practices
• Good understanding of security, privacy, and compliance principles

Nice to Have

• Knowledge of software architecture principles
• Experience with cloud operating models (IaaS, CaaS, PaaS)
• Certificate management automation (e.g. Cert Manager)
• Experience with TypeScript and React
• Backend-for-frontend (BFF) development, including secure API design
• Familiarity with developer portal tools such as Backstage
• About You
• Experience working on production-grade platforms (cloud, infrastructure, or developer experience teams)
• Proven track record building and operating mission-critical systems
• Strong communication and collaboration skills

5V Tech are acting as an Employment Agency for the purposes of this job vacancy. We offer a reward scheme if you can recommend someone for this position, up to €250 for you and an additional €250 to a charity of your choice, 5V Tech are recognised talent solutions experts within IoT and Deep Tech working across Europe, the UK, and North America.