Software Development Engineer in Test (Back-End)

Location: Warsaw, Mazowieckie, Poland X-FLOW is a mobile game development company established in 2018. We gained recognition after the release of Happy Color , the most popular digital coloring book and one of the most successful ad-driven mobile apps in the world. We are looking for a Software Development Engineer in Test (Back-End) to join our team. We need a skilled Engineer who can design, develop, and maintain reliable automated testing solutions, improve test coverage, and help ensure the quality and stability of our products. We are looking for someone who is particularly strong at developing automation frameworks, creating and maintaining automated test scripts, identifying potential issues, and integrating automated tests into CI/CD pipelines. At the same time, we expect a solid understanding of software testing principles, programming fundamentals, and the entire quality assurance lifecycle, along with the ability to collaborate closely with developers and QA engineers to continuously improve our testing processes. Key Responsibilities: Design, develop and maintain test frameworks (backend, load and chaos testing), including setting standards and best practices. Integrate testing and static analysis into CI/CD pipelines (linters, code style and security checks, dependency scanning) and maintain stable quality gates. Review development code and apply white-box testing to improve code quality and testability. Design, develop and maintain observability standards and shared libraries (logging, tracing, metrics, profiling), including setting best practices and onboarding guidelines for product teams. Work closely with development and DevOps/SRE teams to reduce test and quality debt, improve testability of services, and enhance developer experience (DX) through fast feedback loops Requirements: 5+ years in QA Automation, including 5+ years of backend development or testing with Go, Python or JavaScript. Experience building test frameworks from scratch using best practices, with a solid understanding of layered architecture for both backend services and test frameworks. Experience with REST/gRPC API testing, working with schemas (OpenAPI/Swagger, Protobuf) and client generation. Hands-on experience with log analysis, load test result analysis, profiling and troubleshooting performance issues using observability tools (logs, metrics, tracing). Experience with GitLab CI, artifact management, sharding/parallelism, retries and pipeline containerization. Experience with Docker and Kubernetes (k8s); familiarity with basic AWS services for test environments. Experience using AI tools in development and testing, including creating skills and workflows for AI agents. Russian - C1 level. What We Offer: Competitive salary and benefits package. Opportunity to work with a talented and passionate team in a creative and dynamic environment. Flexible working hours and remote/office work options. Career growth and professional development opportunities. A fun and inclusive company culture that celebrates diversity and creativity. Join us and let’s create great content together! When you apply for this role, we process your personal data in accordance with our Candidate Privacy Notice ( https://xflowgames.com/candidate-privacy-notice ).