Polymarket is the world’s largest prediction market platform, enabling individuals to express views on real-world events by trading on outcomes across politics, economics, sports, culture, and current affairs. Built as a peer-to-peer marketplace with no centralized “house,” Polymarket aggregates diverse opinions into transparent, market-based probabilities that reflect collective expectations about the future. We're growing fast – both in terms of volume ($21B traded in 2025) and adoption as an alternative news source. Our ambition is to become a ubiquitous beacon of truth in global media. Polymarket is looking for a Senior QA Engineer to help build the quality assurance function from the ground up. You'll define how we test, what we test, and when code is ready to ship. This means building automated test infrastructure, establishing release processes, and hiring a small team to scale the function. This is a foundational hire; you're coming in to decide what quality looks like at Polymarket. What you’ll do: Build automated test suites from scratch covering web, backend APIs, and critical trading flows (recommend TypeScript and Playwright). Define and own the release testing process, working with the TPM to ensure releases are structured, tested, and shipping fast. Deeply understand the product to identify what to test, including trading flows, market creation, settlement, and edge cases. Integrate automated tests into the deployment pipeline for early issue detection. Use Linear to track issues, coordinate with engineering on fixes, and maintain visibility into quality metrics. As we grow, hire and mentor 2-3 additional QA engineers to build out the function.