Senior Software Engineer in Test IV; Python

Company at a Glance

OpenX is focused on unleashing the full economic potential of digital media companies. We do this by making digital advertising markets and technologies that are designed to deliver optimal value to publishers and advertisers on every ad served across all screens.

At OpenX, we have built a team that is uniquely experienced in designing and operating high‑scale ad marketplaces, and we are constantly on the lookout for thoughtful, creative executors who are as fascinated as we are about finding new ways to apply a blend of market design, technical innovation, operational excellence, and empathetic partner service to the frontiers of digital advertising.

At OpenX Poland, we’re looking for talented, communicative, and curious engineers to join our team in Cracow, Poland. Currently, we’re looking for a Software Developer in Test IV.
Temporary backfill until August 31, 2027.

Our exchange handles billions of ad requests daily, connecting thousands of publishers with demand partners across the global advertising ecosystem.

You will be part of a product engineering team focused on business‑critical workflows that support how advertising transactions are configured, processed, and validated across OpenX. As an SDET IV, you will take ownership of quality for business logic, backend APIs, data flows, and cross‑system integrations. You will design and improve automated test coverage, identify risks early, support CI/CD and release readiness, and help the team ensure that platform behavior remains consistent with business requirements and financial processes.

You will join a cross‑functional product engineering team with a dedicated Product Manager, Scrum Master, Engineering Manager, QA engineers, frontend and backend engineers, and support from data analysts and UX designers when needed. This setup gives you direct access to product context and a real opportunity to influence business requirements, solution design, test strategy, and release quality.

• Analytical – able to connect business requirements, system behavior, and product risk.
• Open‑minded – happy to give and receive feedback, not afraid to fail, and move on.
• Proactive – always looking for practical solutions and ways to move forward.
• Self‑organized and self‑motivated.

• Employment contract  PLN gross/monthly) OR B2B (181 zł - 202 zł PLN net/hourly)
• Working with the newest technologies such as Cloud Computing (GCP)
• Challenges at work that are difficult to find anywhere else!
• Solving important problems in a scale
• Joining a company that is growing and scaling
• Flexible working hours & remote work option

• Validate backend business logic in large‑scale event processing systems running in the cloud, ensuring it behaves consistently with business requirements and financial processes.
• Test backend APIs, data flows, and cross‑system integrations that support business‑critical workflows.
• Build domain understanding and analyse requirements, business rules, and technical designs to identify meaningful test scenarios, edge cases, and risks.
• Read, analyze, debug, and reason about application and test code to investigate issues and understand system behavior.
• Create, maintain, and improve automated test suites and test frameworks.
• Monitor and maintain QA CI pipelines and support continuous delivery.
• Conduct root cause analysis of issues and provide solutions for better coverage and maintainability.
• Collaborate closely with engineers, Product, QA, and other stakeholders throughout the full development lifecycle.

• 5+ years of experience in test automation and software testing.
• Strong Python skills for test automation, debugging, and framework maintenance.
• Experience testing backend APIs and business logic.
• Experience creating, maintaining, and improving automated test suites or test frameworks.
• Experience with CI/CD tools such as Jenkins, Spinnaker, or Cloud Build.
• Ability to read, analyze, debug, and reason about application or test code.
• Excellent troubleshooting skills to triage complex issues.
• Strong communication skills, including the ability to raise risks, ask clarifying questions,…