Senior Engineer I (Auth

Menlo Security is the leader in Browser Security for human and agentic work forces. Our mission is to enable humans and agents to connect, communicate, and collaborate securely, without compromise. The Menlo Browser Security Platform protects organizations from cyberattacks by stopping threats across the web, documents, and email before they reach the user. With Menlo Agent Runtime Security (MARS), that protection now extends to the AI agents working alongside every employee.

Menlo Security is trusted by major global businesses, including Fortune 500 companies and government agencies, to protect their most valuable asset, their data, and is backed by top-tier investors.

Menlo Security is hiring a Senior Software Engineer to own and evolve our Authentication Service — the layer that every user request and AI agent request flows through before anything else happens. Authentication is foundational to how our browser security product works, which means the decisions made here have direct consequences for security posture, system performance, and how Menlo's platform can grow.

You will work with a team that has deep context on this system, taking full ownership from design through deployment on services that protect enterprise customers s role sits at the intersection of systems engineering and security, and it is increasingly central to how Menlo secures AI agent access in enterprise environments — a fast-moving and technically interesting problem space.

Key Outcome(s) Owned:

• Reliable, secure, and performant authentication services that correctly handle every user and AI agent request flowing through the Menlo platform.

• Full lifecycle ownership of assigned services, from design and implementation through deployment and ongoing operation.

Success Metrics / KPIs: (drafted for hiring manager review and adjustment)

• Authentication service availability and latency meeting or exceeding defined SLOs under production load.

• Zero critical security vulnerabilities shipped to production in owned code, measured by post-release security review outcomes.

• Test coverage and failure-scenario validation maintained or improved across owned code paths.

• Features delivered on committed roadmap dates, with defect and rollback rates tracked post-release.

• AI agent authentication capabilities shipped in alignment with the Agentic protection roadmap.

• Design, build, and own production services in the Authentication Service, with direct responsibility for correctness, scalability, and security from day one.

• Develop and extend Menlo's AI agent authentication capabilities, ensuring the platform can securely govern how AI agents authenticate and access enterprise resources.

• Optimize for latency and throughput in networked applications, using profiling tools and efficient concurrency models to handle demanding production workloads.

• Apply rigorous security engineering practices — including threat modeling and vulnerability mitigation — to protect data integrity across distributed environments.

• Use AI coding and debugging tools as part of your development workflow, while critically evaluating outputs for correctness, security implications, and long-term architectural fit before they land in production.

• Partner cross-functionally with product, security, and AI engineering teams to ship authentication capabilities end to end.

• Write comprehensive unit and integration tests covering failure scenarios, and conduct code and design reviews for peers.

Required:

• 3+ years of experience building and operating production systems.

• Hands-on experience in Rust, Python, or Go in a production environment.

• Demonstrated ability to optimize networked applications for latency and throughput using profiling and concurrency techniques.

• Strong background in security-oriented engineering: threat modeling, vulnerability mitigation, and data integrity in distributed systems.

• Track record of comprehensive testing — unit, integration, and failure-scenario coverage — as a normal part of shipping.

• Practical fluency with AI coding assistants, with the judgment to critically assess outputs rather than accepting them…