URGENT (Backend Engineers)

Our client operates one of Japan's largest and fastest-growing cultural marketplace platforms, serving over 6 million monthly users with an exceedingly large amount of annual GMV.

Background for This Hire
The platform is entering its 8th year, and rapid growth has resulted in an extremely large codebase. The monolithic architecture can no longer handle the complexity at scale, and the team is now actively pursuing a modular monolith migration to rebuild a more flexible, sustainable system. They are looking for engineers who can go beyond traditional API development, someone who can design with a strong awareness of DDD and module boundaries, and that can collaboratively build a robust and maintainable architecture. This position is expected to serve as a core member driving the migration while also contributing to feature development.

Responsibilities

• Driving the modular monolith migration: designing and implementing with module boundaries in mind, redesigning existing code, and building robust systems based on DDD
• Improving performance and scalability: designing and implementing APIs capable of handling 10,000+ rps, leveraging async processing and caching, and query performance tuning
• Resolving technical debt: driving large-scale refactoring, library updates, and other initiatives that contribute to the sustainable growth of the service
• New feature development

What Makes This Role Attractive

• Deeply involved in a large-scale re-architecture that underpins the entire service, not just feature additions
• Demands a high level of design and refactoring expertise — redesigning tens of thousands of lines of code into thousands
• Small, senior team where you lead product-focused development that prioritizes outcomes from both a business and technical perspective

Tech Stack

• Languages: Go / TypeScript
• Frameworks: Next.js (App Router) / Vue.js
• Infrastructure: AWS (ECS / Aurora / ElastiCache / S3 / CloudFront / SQS / SNS) / Firebase
• Monitoring: Datadog / Sentry
• CI/CD: GitHub Actions
• AI Tools: Claude Code, Cursor
• Common: GitHub, Notion, Slack

Required Qualifications

• Development experience at a company that builds its own web services in-house
• Backend development experience in Go (3+ years preferred; candidates with 3+ years in Kotlin, Java, Ruby, or Python are also welcome)
• Experience with cloud infrastructure such as AWS or Google Cloud
• Agile development experience collaborating across departments

Preferred Qualifications

• Experience leading a team or project through technical leadership
• Experience re-architecting legacy code
• Practical experience with DDD (Domain-Driven Design)
• Experience designing and tuning table schemas and queries in MySQL with performance and maintainability in mind
• Experience operating services with large-scale traffic exceeding 10,000 rps
• Experience mentoring or managing developers

Ideal Candidate

• Takes initiative and works across technical domains in a small, elite team
• Values DDD-conscious design and wants to be involved in building robust systems
• Engages with the entire value stream and acts with business outcomes as the top priority