Backend & Cloud Engineer

📋 Job Overview

Citadel AI builds software products to evaluate, monitor, and govern AI systems. Our mission is to build trust in AI. We’re located in Tokyo, but we have an international team and global customers. Our goal is to build a world-class startup from Japan, and our team members have previously worked at leading companies such as Google, Paidy, Apple, Stripe, and Meta. This is a unique opportunity to join a team in Tokyo building new products for a global market. As an early employee at Citadel AI, you’ll have significant impact and ownership over the growth of our startup. We’re supported by Japan’s best investors and a top-tier enterprise customer base, and are currently scaling our business in the 1 → 10 stage.

🏢 About Citadel AI

Citadel AI is building software products to evaluate, monitor, and govern AI systems. Our mission is to build trust in AI. We’re located in Tokyo, but we have an international team and global customers. Our goal is to build a world-class startup from Japan, and our team members have previously worked at leading companies such as Google, Paidy, Apple, Stripe, and Meta. We’re currently scaling our business in the 1 → 10 stage.

🎯 The Role

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.

✅ Key Responsibilities

• Design, build, and maintain cloud infrastructure for our hosted products and self-hosted deployments
• Optimize system latency, cost, availability, and scalability
• Develop and improve monitoring, incident response, and deployment infrastructure
• Build backend functionality using web servers, SQL databases, and API design
• Develop features using LLM/AI libraries and GPU inference infrastructure
• Integrate with external services and support self-hosted deployments on Azure and AWS

📌 Required Qualifications

• At least 3 years of experience in cloud infrastructure and/or backend engineering
• Expertise in a cloud platform or technical stack of your choice
• Business-level English and Japanese communication skills
• Ability to adapt and learn new technologies and market environments quickly

⭐ Desirable Experience

• Previous experience working at a startup
• Experience with AI/ML/LLM technologies

🎁 Benefits

Competitive salary and benefits package. Specific details not provided in the job description.

🛂 Visa & Eligibility

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