Senior Software Engineer — AI/LLM Products | Tokyo

◆Role Overview

This role is focused on building AI-powered tools that support sales enablement. As a Software Engineer, you will work on designing and developing product features that leverage AI technologies to improve how sales teams operate and create value for users. This is a high-impact position for engineers who are excited to work at the intersection of product development and applied AI.

◆Technologies

Core Stack

• AI/LLM: OpenAI SDK, prompt engineering & optimization
• Backend: Node.js, TypeScript, Effect (functional TypeScript)
• Cloud: AWS (Lambda, DynamoDB, SQS, SNS, SES, CDK)
• Integrations: Google APIs (Gmail, Calendar), Microsoft Graph API, Zoom API
• Testing: Vitest
• CI/CD: GitHub Actions, pnpm
• The above technologies reflect our current stack. The team has the autonomy to make technology choices that best serve our AI-native product goals. You will be involved from the architecture and technology selection stage.

◆Key Responsibilities

• Design, build, and operate AI-powered systems leveraging large language models (LLMs), including prompt engineering, output parsing, and evaluation pipelines
• Architect event-driven workflows (Lambda, webhooks, queues) that enable AI-powered features to operate reliably at scale
• Collaborate closely with product, sales, and CS teams to translate business needs into effective AI-driven product features
• Own the full lifecycle of AI-powered products — from prototyping and prompt tuning to production deployment and monitoring
• Evaluate and integrate emerging AI capabilities (models, APIs, tooling) to continuously improve product and model performance
• Contribute to engineering best practices through code reviews, documentation, and knowledge sharing

■Required Skills/experience

• 4+ years of software engineering experience in product development
• Hands-on experience building applications that integrate LLMs (e.g., Claude, GPT) — including prompt design, tuning, and output evaluation
• End-to-end engineering experience from design and development through to production operation
• Solid backend engineering skills
• Experience with event-driven or serverless architectures (Lambda, webhooks, message queues)
• Business-level proficiency in both Japanese and English (JLPT N2 or higher certification is required).

■Nice-to-have

• Experience designing, building, and operating architectures on AWS
• Familiarity with RAG (Retrieval-Augmented Generation) patterns, vector databases, or embedding-based search
• Experience building multi-step AI workflows (e.g., tool use, chain-of-thought, planning)
• Knowledge of SOLID principles, Clean Architecture, or Domain-Driven Design (DDD)
• Test-Driven Development (TDD) experience

【Annual salary】

JPY 8,000,000 〜 JPY 10,000,000

Job ID: VAC-288789