Senior Software Engineer, Platform API - Ruby on Rails

Treasure AI Minato-ku, Tokyo April 15 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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Meet Treasure AI's Developers

David discusses how he enjoys switching hats between ML and software, and why he finds Treasure AI’s “extensive ecosystem” so much fun.

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Carlo, a Staff Software Engineer, shares how Treasure AI’s latest AI initiatives are opening up unprecedented opportunities for both the company, and his career.

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Tyler is a software engineer at Treasure AI working on their Data Clean Room product. He talks about how Treasure AI supports their team’s learning and growth, and how they invest in the quality and performance of their services.

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