Senior Quality Assurance Engineer (Trading) at Startale

About the role In partnership with SBI Group, we are building a next-generation decentralized exchange (DEX) aimed at bringing the majority of Japanese equities on-chain. Our goal is to create a secure, transparent, and high-performance trading infrastructure capable of supporting institutional volumes while remaining accessible to retail participants. The platform features a fully on-chain order book and is powered by a custom state transition function and consensus layer, purpose-built for low-latency, high-throughput trading. As the Senior QA Engineer, you will be the quality champion for this system and cover core trading flows, order book behavior, matching logic, and backend services powering execution. As the first senior-level QA on the team, you will own the end-to-end quality strategy with a strong emphasis on automation, ensuring the correctness, reliability, and performance of both API and E2E layers under real-world trading conditions. This is a hands-on role focused on building robust E2E and API test coverage, not manual testing. Key responsibilities • Quality strategy & process: Define and evolve QA standards, release criteria, and quality metrics tailored to a trading platform. Establish best practices for validating execution accuracy, pricing, and API reliability. • Automation (E2E-first approach): Design, build, and maintain a scalable end-to-end automation framework for the web app, covering critical user journeys. • API testing & validation: Develop comprehensive automated tests for backend services and APIs. Ensure consistency between API responses and frontend behavior. • Trading logic validation: Validate correctness of execution paths, price impact, and fee calculations across different trading pairs and liquidity sources. • Performance & reliability: Drive API-level load and stress testing for high-throughput scenarios. Validate system behavior under peak traffic and degraded conditions (timeouts, partial failures, node issues). • Test data & environment strategy: Design reliable test environments and datasets (mocked or real blockchain interactions), ensuring repeatability of E2E and API tests. • Cross-team collaboration & leadership: Work closely with Engineering and Product to define testable acceptance criteria. Take ownership of QA processes, drive automation adoption, and set quality standards across the team. Qualifications Required experiences • 3+ years in QA for web or fintech products, with at least 2+ years focused on test automation and E2E testing. • Strong experience building and maintaining E2E test frameworks (e.g. Playwright, Cypress, or similar). • Solid experience in API testing and automation (REST, JSON-RPC, or similar). • Strong JavaScript/TypeScript skills. • Experience testing complex transactional or financial systems. • Good understanding of trading concepts: slippage, liquidity, routing paths, execution flow. • Experience designing stable, maintainable automated test suites (CI integration, flakiness reduction). Nice-to-have • Experience testing DEXs, trading platforms, or financial systems. • Familiarity with blockchain basics, smart contracts, and on-chain transaction flows. • Understanding of AMMs, liquidity pools, and routing algorithms. • Experience with performance/API load testing tools (e.g. k6, Artillery). • Experience using AI tools to improve test generation and coverage.