Backend & Cloud Engineer

Citadel AI Shibuya-ku, Tokyo July 30 2026
  • 💴 No salary range given
  • 🏡
    Partially remote
  • 🗾 Japan residents only
  • 💬
    Business Japanese
    Business English
  • 🧪
    Intermediate level
    3+ years experience required
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About Citadel AI

Citadel AI Shibuya-ku, Tokyo

Citadel AI builds products to test and monitor high-risk AI systems. Our mission is to make the world's AI systems more reliable and trustworthy.

Key benefits

  • International team and global customers
  • World-class engineering team
  • Significant ownership and impact

About the position

We’re hiring a backend engineer to work with our small, full-stack team to build cloud infrastructure and products to evaluate, monitor, and govern AI systems.

You’ll have a wide range of responsibilities across our cloud infrastructure and product backend. On the cloud infrastructure side, you’ll work on latency and cost optimization, scalability, monitoring, and deployments. On the product side, you’ll work with web servers, SQL databases, LLM/AI libraries, GPU inference, API design, integrating with external services (e.g. SSO), and general product functionality to govern AI models and agents.

We primarily run on Google Cloud for our hosted products (mostly Compute Engine, Cloud Run, Cloud Build, Artifact Registry, Vertex AI), but also support self-hosted deployments on Azure and AWS. Our backend is primarily in Python. Some technologies we use are: Docker, Helm, Tilt, OpenTofu, PostgreSQL, Redis, FastAPI, Flask.

Responsibilities

You’ll have a wide range of responsibilities across our cloud infrastructure and product backend. On the cloud infrastructure side, you’ll work on latency and cost optimization, scalability, monitoring, and deployments. On the product side, you’ll work with web servers, SQL databases, LLM/AI libraries, GPU inference, API design, integrating with external services (e.g. SSO), and general product functionality to govern AI models and agents.

Requirements

Our company, technology, and market are new and changing rapidly, so a large part of the job is to adapt and learn new things. We value learning fast over pre-existing knowledge (“slope is more important than y-intercept”).

You should have at least 3 years of experience in cloud infrastructure and/or backend engineering. We don’t require experience in GCP or Python specifically, but we expect you to be an expert in the cloud platform or technical stack of your choice.

Business-level English and Japanese are required. We prioritize candidates in Tokyo, but may consider remote for exceptional candidates.

Nice to haves

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

You’ve worked at a startup before, or you have AI/ML/LLM experience.

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