Platform Security Engineer - Mercari - Mercari, inc.

Job Duties

• Automate security controls and monitoring across Mercari’s platform to enable secure-by-default operations.
• Develop technical solutions to prevent or mitigate security vulnerabilities and strengthen overall system security.
• Maintain technical and security standards for production and corporate infrastructure services.
• Collaborate with security management, legal, and internal auditors on technical security matters.
• Work with platform engineering teams to balance security with other requirements.
• Review architecture proposals (infrastructure, data flows) and propose security controls to minimize risk.
• Operate in a “security as code” mindset, emphasizing automation and scalable security practices.

Technical Stack

Essential Skills

• Solid grasp of core security concepts (CIA, least privilege, authentication vs authorization, cryptography, secure protocols, application security).
• Practical use of Git, GitHub, CI/CD (GitHub Actions), and shell scripting.
• Programming experience in Go, Python, or TypeScript.
• Experience with cloud platforms (GCP, AWS, Azure), containers (Docker, Kubernetes), and Infrastructure as Code (Terraform).
• UNIX-like systems administration and hardening; proficient with POSIX utilities.

Nice-to-have Skills

• 4+ years in security roles;Bachelor’s in Computer Science or equivalent.
• Familiarity with cloud/web app architecture and Secure SDLC (SLSA).
• SQL knowledge (BigQuery, Postgres); cryptography concepts (key management, TLS, KMS, PKIs).
• Networking knowledge (TCP/UDP, DNS, HTTP); identity federation (OIDC, SAML).
• PCI-DSS or similar standards; Japanese (basic) and English (independent) language skills.

Career Growth Perspective

• Opportunity to shape security across a large platform, gaining impact at scale and exposure to cutting-edge cloud and automation technologies.
• Strong emphasis on “security as code” and automation, accelerating growth in SecDevOps, cloud security, and IaC disciplines.
• Cross-functional collaboration with security, legal, and product teams, providing broad governance, risk, and compliance experience.
• Clear path toward senior/lead security engineering, security architecture, threat modeling, and incident response roles, with potential for multi-cloud specialization and language skills development.