Senior Software Engineer, Security

• 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.

We're hiring our first security engineers. Both report directly to the CTO.

We want software engineers with security as their superpower, not security specialists who occasionally write code. The distinction matters here. At our size, the only way one person covers a surface this large is to build things that keep working after they move on. A findings queue you work through by hand grows faster than you can close it. A guardrail in the deployment pipeline doesn't.

The work is product and infrastructure security: making the paths that move money hard to attack, and making the secure way to build something also the easy way. The ledger and its write path, card issuing, payouts, and our stablecoin work are the systems that matter most. The job runs in both directions. You'll be in design review early on anything new, and you'll be continuously assessing what we've already shipped, because most of Flex's risk lives in code that exists today.