Senior Software Engineer, Backend

About this role

Flex is building the AI-native private bank for business owners . We’re re-architecting the entire financial system for entrepreneurs—from the first dollar a business earns to how that value compounds, moves, and is ultimately spent in real life. Banking, credit, payments, personal finance, and financial operations—rebuilt from the ground up as a single, intelligent system. Flex is the full financial home for ambitious owners. Since launching publicly in September 2023 , Flex has scaled from zero to nine-figure annualized revenue , with a clear path to profitability by late 2026 . We move fast, ship relentlessly, and operate with extreme ownership. Our customers are affluent business owners ($3–$200M in revenue) —the backbone of the economy and one of the most underserved segments in finance. They’re stuck with outdated banks and fragmented tools. We’re replacing all of it. The opportunity is massive: a ~$1T+ revenue market hiding in plain sight. Our ambition is to build a $100B+ company by delivering a product that is fundamentally better—not incrementally improved. Flex has raised $100M+ in equity and $300M+ in debt. - Mission-critical problems : We build software that directly controls how money moves at scale. - High bar, low ego : Small teams, exceptional people, real ownership. - Speed over comfort : We prioritize execution, quality, clarity, and results. - Enduring impact : What we’re building will define how a generation of owners runs their businesses. Team & Locations We hire exceptional people who want to build hard things and see their work matter immediately. Roles are available in: San Francisco, Miami, New York, and fully remote. Flex Fuels Ambition. The Role We are looking for engineers who are excited to be part of our early story and help us build a diverse and vibrant company. As a senior software engineer you will have the opportunity to work across the entire stack with a focus on the back-end. You will have the opportunity to learn and drive th