Tokyo ビルドプラス(旧ウォールアンドケース)
About the Role
We are seeking a Senior Software Engineer to help lead the evolution of a large-scale, revenue-critical platform.

You will work within an established Ruby on Rails monolith while helping design and implement a long-term transition toward a Service-Oriented Architecture.

This is a high-impact role where you will influence architecture, mentor engineers, and drive technical strategy.
What You'll Do
Work within an existing monolith, identify proper domain boundaries, and ensure safe, well-tested changes.
Lead the design and development of new services, including domain modeling, API design, and technology selection.
Guide engineers, structure project deliverables, and raise engineering standards across the organization.
Drive operational excellence through observability, monitoring, logging, alerting, and zero-downtime deployment practices.

Requirements

Expertise in modern statically typed languages (e.g., Go, Kotlin, Scala, Rust, C#) with deep understanding of concurrency and asynchronous paradigms.

Experience building and maintaining services in a Service-Oriented Architecture, as well as maintaining or refactoring monolithic systems.
Hands-on experience creating and maintaining CI/CD pipelines and implementing zero-downtime deploys.
Strong understanding of scalable storage technologies (e.g., Cassandra, AWS Aurora).
Proficiency with observability tools (Datadog, Grafana, Prometheus, etc.).
Conversational Japanese (日本語必須)
Strong communication skills and the ability to explain complex concepts clearly in English
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