Senior Software Development Engineer in Test (SDET)

Flex is a growth-stage, NYC headquartered FinTech company that is building the payment layer for life's financial obligations, giving households one place to see, split, and pay their bills around how they live and get paid. By offering greater choice over how and when payments are made and allowing eligible on time payments to help build a positive credit history, Flex puts households back in control of their cash flow.

That work brings together people with different perspectives who challenge the status quo and take ownership of solving difficult problems. For you, that means doing the best work of your career next to people who make you better, and together bringing ideas to life that make a real impact for the people we serve.

About the role

As a Senior SDET at Flex, you will own the test automation and quality efforts for entire product areas or major features. You will architect and optimize automation frameworks, lead test strategy for complex systems, and regularly collaborate across teams to deliver reliable and high-quality releases. This role offers the opportunity to mentor others, drive cross-functional quality improvements, and play a critical part in shaping the future of our engineering excellence.

What you’ll do

Architect, implement, and optimize automated test frameworks for complex product areas, ensuring high reliability and maintainability

Design, develop, and maintain robust automated test suites for API, UI, and integration testing, with Playwright as our primary end-to-end automation framework

Design, build, and run performance, load, and stress tests using k6, defining performance baselines and thresholds for critical user flows and APIs

Lead test strategy development and perform risk analysis for major features and systems

Integrate automated testing, including performance tests with pass/fail thresholds, into CI/CD pipelines, supporting continuous integration and delivery processes

Proactively identify systemic quality issues and drive cross-team process improvements to increase coverage and efficiency

Analyze test coverage, identify gaps, and implement solutions to improve product quality

Collaborate closely with engineering, product, and quality leaders on cross-functional quality initiatives and release planning

Provide technical guidance and mentorship to junior SDETs and QA team members, fostering skill development and best practices

Review code and test cases contributed by other engineers for quality and maintainability

Maintain accurate and actionable test documentation, reports, and quality metrics for assigned product areas

Investigate and resolve complex defects and production issues through advanced debugging and root cause analysis

Advocate for quality and champion adoption of best practices within and across engineering teams

Proven ability to lead test strategy and risk analysis while making high-impact technical decisions amid ambiguity and prioritizing what matters most.

Key qualifications

Bachelor’s degree in Computer Science or related field, or equivalent experience

5+ years of experience in software development and test automation

Advanced proficiency in multiple programming languages and test automation frameworks

Deep experience designing, building, and maintaining automation frameworks (e.g., Playwright, Cypress, Selenium, RestAssured)

Strong expertise in API, UI, and integration testing

Strong, hands-on Playwright automation experience, including building scalable, maintainable, and stable suites (page objects, fixtures, parallelization, flaky-test reduction, and CI execution)

Hands-on experience with performance and load testing using k6 (scripting scenarios, defining thresholds, and analyzing results to find bottlenecks) * Strong expertise in API, UI, and integration testing

Proficient in CI/CD pipeline integration and optimization

Skilled in test strategy development, risk analysis, and test architecture

Advanced debugging, troubleshooting, and root cause analysis

Solid understanding of database systems and advanced SQL

Experience with observability and monitoring tools (e.g., DataDog, NewRelic), including correlating performance test results with application metrics and traces

Excellent cross-functional communication and mentorship skills

Strong written and verbal communication skills; able to collaborate across functions

Compensation

Flex takes a market-based approach to pay, and compensation may vary depending on your primary work location. Work locations are categorized into one of three tiers based on a cost of labor index for that geographic area. The successful candidate’s starting pay will be commensurate with their experience, qualifications, and Flex’s internal leveling guidelines and benchmarks.

Tier 1 (NYC/Bay Area, Los Angeles, Seattle)$136,000—$170,000 USDTier 2 (Austin, Washington D.C. Philadelphia, San Diego, Chicago, Atlanta)$122,400—$153,000 USDTier 3 (Salt Lake City, all other USA cities)$115,600—$144,500 USD

Life at Flex

Building a successful company takes a diverse team of intelligent, curious, determined, empathetic, and self-aware people. Our headquarters is in New York City, with employees across the US, Australia, Canada, and South America. We’re growing quickly and deliberately, with a focus on building an inclusive culture. We value the perspectives our people bring and take pride in being an equal opportunity workplace.

Offices

Roles posted in New York, San Francisco, and Salt Lake City are hybrid positions with on-site expectations of 2-3 days per week in our local offices. For candidates outside of these areas, you may be eligible for our relocation assistance program.

Benefits

View our benefits and more at getflex.com/careers.