Minatomirai Station | Backend Engineer @ AI startup

Backend Engineer (API Gateway + Routing + Rate Limiting)

Role overview

As a Backend Engineer for API Gateway and Core Services, you will build the control-plane and gateway layer that sits between customers and our serving infrastructure. You will own authentication and tenancy boundaries, request validation, routing to the right model endpoints, quota and rate limit enforcement, and reliability mechanisms that keep the platform stable under load. This role is not just “building endpoints”—it is building a platform interface that is secure-by-default, abuse-resistant, and operable at scale.

You will collaborate with serving/runtime engineers, infrastructure operations, and networking to ensure routing decisions reflect real capacity and failure domains, and that the system exposes the right telemetry for rapid debugging.

Responsibilities

• Build and maintain gateway semantics: streaming correctness, stable API contracts, consistent error models, versioning strategy, and predictable timeout/backpressure behavior.
• Own identity and tenancy boundaries: API key management, org/project separation, permission integration points, audit logging, and least-privilege defaults.
• Implement dynamic routing: model selection policies, endpoint health-aware routing, tenant-aware prioritization, fallback strategies, and safe degradation behavior.
• Design and implement rate limiting and quotas: per-key/org/model enforcement, burst control, fairness, and abuse prevention hooks with transparent feedback.
• Engineer reliability primitives: idempotency, retries/timeouts, circuit breakers, request shedding, queueing behavior, and progressive rollouts for safe change.
• Integrate observability end-to-end: tracing, request metrics, latency breakdown, error attribution, and usage accounting hooks that support debugging and billing-grade correctness.
• Build internal operator tooling: customer configuration, debugging workflows, incident response tools, and safe admin actions with audit trails.

[Employment Type]
Full-time employee
*Probationary period: 3 months

[Salary]
Annual Salary: ¥8,000,000 - ¥14,000,000
Monthly Salary: ¥666,667 - ¥1,166,667 (Monthly Base Salary: ¥666,667 - ¥1,166,667)
■Salary Increases: Available

[Working Hours]
9:00 AM - 6:00 PM (60-minute break)

[Work Location]
Queen's Tower A, 10th Floor, 2-3-1 Minatomirai, Nishi-ku, Yokohama, Kanagawa Prefecture, 220-6010
■Access: 7-minute walk from Sakuragicho Station (all lines), direct access from Minatomirai Station (Toyoko Line, Minatomirai Line)
■Non-smoking workplace
■Changes to work location: Company-designated offices
■Transfers/Secondments: None

[Holidays and Leave]

120 days off per year Days
Full two-day weekend
Annual paid vacation (minimum 10 days after the seventh month of employment)

[Benefits]
Partial transportation allowance (up to ¥15,000 per month)
Social insurance (health insurance, employee pension insurance, employment insurance, workers' compensation insurance)
Overtime pay: Standard overtime pay

Requirements

• 5+ years backend engineering delivering high-availability production APIs.
• Strong distributed systems fundamentals and experience designing for operability (telemetry, debuggability, safe rollouts).
• Experience implementing routing, rate limiting, or multi-tenant control planes with rigorous correctness expectations.
• Strong security mindset: least privilege, secure defaults, and auditable operational actions.
• Strong written communication and attention to detail—API behavior is a contract.