▍Why We Are Hiring Our product API is Python (FastAPI); 780 pull requests were merged in the last 30 days (measured 2026-09-12). You design how the team verifies changes at this pace, and shape the backend architecture as SalesNow approaches Series B. AI increased how much code we ship; engineers judge whether a change fits the architecture and the data. ▍Problems You Will Work On ・Reduce full reindexing time on our OpenSearch platform: 105M documents (~460 GB). You redesign the source-side DB queries and the ingestion ・Break up a 2,800-line model layer without stopping the service (Strangler Fig, feature flags, API versioning) ▍Responsibilities ・Backend development of AI and data features in Python (FastAPI) and TypeScript ・Design, PoC, and production implementation of LLM features over company data ・Fast iteration with PdMs; refactoring APIs and data models at scale ・Verifying edge-case behavior, quality, reproducibility ・Stack: PostgreSQL, OpenSearch, AWS, Claude Code, Codex, Cursor, CodeRabbit ※Scope of changes to duties: yes（従事すべき業務の変更の範囲：有り） ▍Requirements ・Currently residing in Japan, or willing and able to relocate to Japan ・Business-level Japanese communication skills (JLPT N1 or higher) ・Backend development experience for web or mobile applications ・Experience designing backend APIs and databases ・Agile development at an operating company; code and design reviews ▍Nice to Have ・Leading technology selection and architecture design / Data processing with generative AI ・Defining requirements with stakeholders / Startup or 0→1 product development / Data platforms and cloud infrastructure ▍Why Join Us 【1】Ship LLM features on 16 million+ corporate profiles backed by 8 billion records. You own accuracy and cost in production. 【2】Redesign search at the scale of 100 million documents. 【3】Decide architecture with leadership that also writes code. ▍Hiring Process Application screening → Interviews (multiple rounds) → Reference check → Offer meeting (job offer)