Infrastructure Engineer

Flex was founded to solve a simple but costly problem: making it easy for health and wellness brands to accept HSA and FSA payments online. We're backed by First Round, Core VC, Rethink Capital power checkout for Equinox, Dermstore, Therabody, and Ultrahuman to name a few. For years, only giants like Amazon and Walmart could process these payments at checkout, leaving smaller merchants - and their customers - to deal with frustrating reimbursement paperwork.

Our technology verifies product eligibility in real time, handles split payments for eligible and non-eligible items, and can even issue Letters of Medical Necessity during checkout. With $150 billion in annual HSA/FSA spending potential, we’re giving brands the tools to unlock new revenue and making it easier for consumers to use the benefits they’ve earned.

We're looking for an Infrastructure Engineer to design and own the cloud infrastructure, databases, and core systems that every other engineer at Flex builds on. You'll work closely with backend, frontend, and other stakeholders to keep the systems that move real money fast, reliable, and resilient.

This is a role for someone who thrives in ambiguity, takes initiative, and is excited about building at an early-stage company.

• Design, build, and operate the cloud infrastructure, databases, and core systems that engineering teams build on

• Partner with backend, frontend, and other stakeholders to translate their needs into reliable platform capabilities

• Own and improve our cloud infrastructure, databases, and observability stack

• Analyze, troubleshoot, and resolve production issues rooted in infrastructure, scaling, and reliability

• Collaborate on cross-functional projects that connect the full Flex experience, from consumer checkout to merchant analytics

• Create and maintain documentation for infrastructure, platform services, and on-call runbooks

• Contribute to a culture of learning, problem-solving, and operational excellence

• You have 5+ years of experience building and operating production infrastructure at scale

• You have hands-on experience with AWS, database operations and tuning (Postgres or similar), and infrastructure as code (Terraform or similar)

• 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

• Experience operating Rust services in production

• Background in payments, fintech, or health benefits (HSA/FSA), or another regulated, money-moving domain

• 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