Job Overview
Location
United States
Job Type
Full-time
Category
Backend Engineer
Date Posted
May 3, 2026
Full Job Description
đź“‹ Description
- • As a Backend Engineer at Withflex Inc., you will design and own the core services and APIs that power Flex’s platform, enabling health and wellness brands to accept HSA and FSA payments seamlessly at checkout.
- • Your day-to-day responsibilities include building and maintaining backend systems for eligibility verification, split payments, and Letter of Medical Necessity (LMN) issuance; modeling complex domains like transactions and consumer accounts; collaborating with frontend, design, and business teams to translate user needs into reliable APIs; improving service architecture and data models; troubleshooting production issues related to data correctness and transactional edge cases; contributing to cross-functional projects; and creating documentation and runbooks to support operational excellence.
- • You will join a mission-driven, early-stage fintech company backed by First Round, Core VC, and Rethink Capital, serving brands like Equinox, Dermstore, Therabody, and Ultrahuman, with a vision to unlock $150B in annual HSA/FSA spending potential.
- • In this role, you will have the opportunity to shape the technical foundation of a high-impact product, gain deep expertise in regulated payments systems, work autonomously in a fast-paced environment, and grow your influence as a key contributor to Flex’s growth and innovation.
🎯 Requirements
- • 5+ years of experience building production backend services and APIs in a typed language (Rust, TypeScript/Node, Go, Python, etc.)
- • Strong relational database fundamentals and experience designing APIs that other teams or external partners depend on
- • Resourceful, curious, and comfortable learning new tools quickly
- • Thrives in fast-paced, dynamic environments and enjoys wearing multiple hats
- • Collaborative and enjoys working across teams to solve problems
- • Execution-minded with a focus on keeping the end user in mind
- • Proficient at leveraging AI tools to ship faster
🏖️ Benefits
- • 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
Skills & Technologies
About Withflex Inc.
Withflex is a technology company focused on revolutionizing the way businesses manage their flexible workforce. Their platform provides a comprehensive solution for hiring, onboarding, managing, and paying contingent workers, freelancers, and contractors. By centralizing these processes, Withflex aims to streamline operations, ensure compliance, and reduce administrative overhead for companies. They cater to businesses of all sizes looking to leverage flexible talent efficiently and effectively, offering tools for talent sourcing, contract management, time tracking, and automated payments. Withflex operates within the HR tech and gig economy enablement sectors.
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