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Flex splits your bills into smaller, stress-free payments throughout the month. Start today with your rent bill!
Backend Engineer
Location
United States
Posted
80 days ago
Salary
$160K - $220K / year
Seniority
Mid Level
Job Description
Backend Engineer
Flex
Role Description We're looking for a Backend Engineer to design and own the services and APIs that power Flex - eligibility verification, split payments, and LMN (letter of medical necessity) issuance at checkout to name a few. You'll work closely with frontend engineers, design, and business stakeholders to build reliable systems that move real money correctly and unlock HSA/FSA spending for merchants and consumers. This is a role for someone who thrives in ambiguity, takes initiative, and is excited about building at an early-stage company. Responsibilities (What You’ll Do) - Design, build, and own backend services and APIs that power Flex’s applications - Model the domain - eligibility rules, transactions, merchants, consumer accounts, etc. - in data structures and APIs that other teams build on - Partner with frontend, design, and business stakeholders to translate merchant and consumer needs into reliable APIs and workflows - Own and improve our backend service architecture, data models, and integrations - Analyze, troubleshoot, and resolve production issues rooted in business logic, data correctness, and transactional edge cases - Collaborate on cross-functional projects that connect the full Flex experience, from consumer checkout to merchant analytics - Create and maintain documentation for APIs, services, and on-call runbooks - Contribute to a culture of learning, problem-solving, and operational excellence Qualifications - You have 5+ years of experience building production backend services and APIs in a typed language (Rust, TypeScript/Node, Go, Python, etc.) - You have strong relational database fundamentals and experience designing APIs that other teams or external partners depend on - You’re resourceful, curious, and comfortable learning new tools quickly - You thrive in fast-paced, dynamic environments and enjoy wearing multiple hats - You’re collaborative and enjoy working across teams to solve problems - You have an execution mindset and always keep the end user in mind - You're proficient at leveraging AI tools to ship faster Requirements - Experience with building systems using Rust - Background in payments, fintech, or health benefits (HSA/FSA), or another regulated, money-moving domain Benefits - A mission-driven team making healthcare spending effortless - Early-stage impact - your work will directly shape our growth and success - Collaborative, high-trust, and transparent culture - Competitive compensation and equity package - Flexible, remote-friendly work environment
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