Senior Software Engineer, Platform API - Ruby on Rails

Treasure AI Minato-ku, Tokyo July 23 2026
  • 💴 No salary range given
  • 🏡
    Partially remote
  • 🗾 Japan residents only
  • 💬
    Conversational Japanese
    Conversational English
  • 🧪
    Senior level
    5+ years experience required
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About Treasure AI

Treasure AI Minato-ku, Tokyo

Treasure AI is the only enterprise Customer Data Platform that harmonizes an organization’s data, insights, and engagement technology stacks to drive relevant, real-time customer experiences throughout the entire customer journey.

Key benefits

  • Highly Technical Founders
  • Globally distributed company
  • Open Source is in our DNA

About the position

Responsibilities

  • Design, ship, and operate Ruby on Rails Platform APIs end-to-end—from spec to rollout—meeting agreed availability/latency SLOs.
  • Drive API design (OpenAPI/contract tests), versioning/deprecation, and compatibility for first-party UIs and partner integrations.
  • Operate across the stack as needed, from backend APIs to front-end experiences, based on product needs.
  • Ensure scalability, performance, and operationalization remain primary concerns throughout development.
  • Keep up to date on novel technical concepts that we should adopt (and which ones we should ignore).
  • Evaluate and introduce pragmatic improvements (framework/library upgrades, testing strategy, CI/CD/IaC) with clear trade-offs—in writing.

Requirements

  • 5+ years of software engineering experience with a proven track record.
  • Have the ability to work full-stack (from the DB all the way to the Frontend).
  • Writing Web APIs in Ruby on Rails.
  • SQL and working with and maintaining Relational Databases in a production environment.
  • System architecture and design
  • Knowledge of design patterns involving APIs that communicate with many backend components.
  • Variety of testing approaches, correctness through design, and a holistic approach to quality.
  • Cloud technologies (particularly AWS) and development/deployment in a cloud infrastructure.
  • Write clear design docs and incident postmortems; communicate across time zones.
  • Comfortable working in English and Japanese: can participate in team meetings, ask/answer questions, and write simple tickets/Slack messages in either language.

Nice to haves

While not specifically required, tell us if you have any of the following.

  • Sense of project ownership and responsibility.
  • Experience owning and leading short to medium-term technical direction across teams
  • Business-level English proficiency and conversational-level Japanese proficiency
  • Experience working in a different programming environment, such as the JVM (Java or Kotlin) or a different API style, such as JSON: API.
  • Contributed to a production-grade web application handling high traffic.
  • Experience in developing a fully managed cloud service.
  • Experience with microservices-oriented architectures and authentication/authorization challenges.
  • Made open source contributions.
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