Backend & Infrastructure Engineer

Role overview Own backend engineering, infrastructure, and security for enterprise systems and an AI SaaS product, from requirements review through production operations. The work focuses on APIs, data, platform foundations, and identity controls, collaborating with a small team and using coding agents as part of the development process.

Responsibilities - Translate screen mockups into validated requirements, data models, authorization rules, APIs, and production designs. - Build and operate cloud infrastructure, including services, databases, messaging, secrets management, infrastructure as code, and deployment pipelines. - Design authentication and authorization, including external identity providers, role-based access, tenant isolation, audit trails, and least-privilege controls. - Integrate and migrate data across core systems, SaaS products, and cloud environments, and establish analytics foundations. - Build backend services for AI features, with safeguards against prompt injection and systems for execution logging and cost visibility. - Operate production systems through monitoring, incident response, and recovery; review coding-agent output and document design decisions.

Requirements - Ability to design, build, and operate production backends in TypeScript/Node.js or Python; five or more years of professional experience is the stated guideline. - Hands-on experience operating production environments on Google Cloud. - Ability to model relational data, plan safe schema changes, and manage migrations, including with PostgreSQL. - Experience implementing OIDC or JWT authentication and role-based access, and testing tenant boundaries. - Experience with Terraform and CI/CD automation for tests and deployments. - Regular use of coding agents, with independent verification and written design documentation for asynchronous teamwork.

Nice to have - Backend operations on AWS or Azure, cross-cloud identity, or external identity integrations using SAML/OIDC. - Experience with BigQuery, enterprise system integrations, SaaS data migration, or LLM-based agents.

Benefits and work setup This is an independent contract role, with a commitment equivalent to at least three days per week; the schedule is negotiable. Work can be remote or from an office in Tokyo. Compensation, contract length, and expenses are discussed during interviews.