[Hiring] Senior Software Engineer @Flex

Role Description

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.

• The work is product and infrastructure security: making the paths that move money hard to attack.
• You'll be in design review early on anything new and continuously assessing what we've already shipped.
• There's no security team above you and no CISO. You'd set the standard here and own the risk decisions that come with it.
• At a company shipping this fast, a security engineer who blocks everything is worse than no security engineer.
• Getting engineers to adopt something matters here as much as finding the problem in the first place.

Qualifications

• You're a strong software engineer first.
• You think like a builder and an attacker at the same time.
• You care about developer experience.
• You can tell a senior colleague that what they built isn't safe and explain why in plain language.
• You're comfortable owning problems end to end with limited guidance.
• You make risk-based calls.
• You can read a system diagram and find the trust boundary nobody drew.
• You write clearly.

Requirements

• Substantial hands-on experience building or securing systems in a fast-moving environment.
• Real software engineering ability in a language we'd ship (Python, Go, TypeScript, or similar).
• Hands-on cloud infrastructure experience: AWS or GCP, Terraform or equivalent IaC.
• Practical threat modeling on systems with real consequences.
• Experience with secrets management, workload identity, and service-to-service authorization.
• Experience handling inbound vulnerability reports.
• Clear written communication and a bias toward writing things down.

Benefits

• Compensation: $170,000 - $230,000 a year, depending on experience, plus equity.
• Build something generational—Capture the full lifecycle of money for ambitious business owners.
• Work on real money, real risk—Payments, credit, and banking at serious scale.
• True ownership—Small teams, high trust, real accountability.
• Founder-level exposure—Direct access to leadership, customers, and investors.
• Real upside—Meaningful equity if you help build something big.