Freelance Software Development Engineer in Test - Backend/API focused

We are looking for a Freelance Software Development Engineer in Test (SDET) to strengthen the quality of our platform by building scalable test automation and tooling with a strong focus on backend services and APIs. You will work alongside engineers, product managers, and DevOps to ensure every release is reliable, observable, and tested end-to-end.

Tasks

• Design and implement automated API and integration tests for backend microservices
• Develop reusable test frameworks and libraries in collaboration with backend engineers
• Maintain test coverage across multiple services , ensuring data consistency and reliability
• Contribute to CI/CD pipelines , integrating automated tests to run at every stage (build, deploy, release)
• Investigate and reproduce complex backend issues , analyzing logs, metrics, and traces to isolate root causes
• Continuously improve test infrastructure and tooling with a focus on scalability and maintainability

Requirements

• 2–4 years of experience in software testing or automation engineering, with strong backend/API focus
• Programming experience in at least one backend language (etc. Java, Kotlin, Go)
• Strong understanding of REST/GraphQL APIs, messaging systems, and event-driven architectures
• Hands-on experience with API testing frameworks (e.g., REST-assured, Ktor, Playwright API, Postman/Newman)
• Experience with CI/CD systems (GitHub Actions, GitLab CI, Jenkins) and version control (Git)
• Practical knowledge of containerized environments (Docker, Kubernetes)
• Strong debugging skills using logs, metrics, and distributed tracing (Datadog, OpenTelemetry, Grafana)
• Solid understanding of QA methodologies (test strategies, defect lifecycle, coverage analysis)

Benefits

• Dynamic workplace: A digital environment with international projects and space to learn and grow
• Flexible work conditions: Hybrid working mode with a tailored remote policy
• Physical space for ideas: A great office space in Berlin Mitte with top-tier equipment

Even if you do not meet every single requirement, we encourage you to apply if you believe you are well-suited for the role and can contribute meaningfully to our team.

About GLS/NXT

GLS/NXT was founded with the mission to build the next generation of logistic experiences driven by technology - core, adjacent & beyond. More specifically, our sphere of interest is the Logistics and eCommerce sector. We are entrepreneurs and hence always start with the user's needs. We are located between Corporate and Startups and leverage the benefits from both (startup speed and corporate muscle). GLS/NXT inhabits different project teams, acting as startups with business responsibility and setting their own vision and mission. GLS/NXT is part of the GLS IT Services GmbH.

Commitment to Diversity

GLS/NXT is an equal opportunity employer, which means we do not discriminate on the basis of race, colour, religion, marital status, age, national origin, ancestry, physical or mental disability, medical condition, pregnancy, genetic information, gender, sexual orientation, gender identity or expression. We celebrate diversity and are committed to creating an inclusive environment for all employees.