Job Details

Senior Product Security Engineer

LMArena is seeking a Senior Product Security Engineer to lead the strategy, design, and hands‑on implementation of systems that protect the integrity of our platform and the trust of our community. You'll work across product, infrastructure, and data pipelines to proactively identify risks, embed security into core features, and build scalable defenses against abuse, fraud and adversarial behavior.

Builder role – you'll not only set technical direction but also write the code, build the tools and design the frameworks that embed security and trust into our product's DNA. Your work will directly influence how the world's top AI labs, developers and users experience LMArena, ensuring we remain resilient in the face of real‑world attacks and evolving threats.

Responsibilities

• Own the product security vision for LMArena, ensuring security and trust are core to every stage of our product lifecycle.
• Design and implement platform‑wide security features, including Sybil resistance, bot detection, reputation systems and anti‑abuse primitives.
• Lead threat modeling and security architecture reviews for new and existing product features.
• Collaborate with infrastructure and product engineering to design secure APIs, data flows and identity systems that scale.
• Improve developer velocity by creating secure‑by‑default frameworks and tooling for internal teams.
• Partner with incident response to assess, contain and remediate security events, and lead deep post‑mortems to improve defenses.
• Stay ahead of emerging attack techniques and apply cutting‑edge security research to our platform.
• Mentor engineers across the company on secure coding practices, architecture trade‑offs and operational security.

Requirements

• 8+ years of experience in software engineering or security engineering, including staff‑level scope in securing large‑scale, user‑facing platforms.
• Proven track record designing and implementing systems to detect, mitigate and prevent adversarial behavior (bots, Sybil attacks, automated abuse).
• Strong experience with threat modeling, secure architecture design and risk assessment.
• Hands‑on experience building security features into production systems at scale (millions of DAU / billions of requests).
• Proficiency in backend development (Node.js, TypeScript, Python or Go) and willingness to work across the stack when needed.
• Strong knowledge of distributed systems security, identity and authentication mechanisms.
• Excellent communication skills, able to build alignment across engineering, product and leadership teams.

Bonus Points

• Experience in adversarial ML, trust & safety systems or securing voting/reputation platforms.
• Familiarity with advanced detection methods, user fingerprinting or behavioral analytics.
• Contributions to open‑source security tools or research.
• Background in securing real‑time, interactive platforms at scale.
• Built real‑time detection systems and post‑processing pipelines to identify attacks on large‑scale systems.

Seniority level – Mid‑Senior
Employment type – Full‑time