Senior Backend Engineer (Python / FastAPI)

What You'll Do

- Own the Python/FastAPI backend end to end, including HTTP APIs, background workers, and production behaviour.

- Own the PostgreSQL data model and its evolution, covering schema design, migrations, concurrency control, and query performance.

- Build asynchronous, event-driven pipelines for medical image processing, from ingestion and de-identification to inference submission and result handling, with reliable retry and timeout behaviour.

- Integrate with an internal platform for authentication, GPU inference, and usage metering, keep the product resilient when it is unavailable, and enforce multi-tenant data isolation and patient data privacy.

- Agree the product-to-model contract with the data science team and define API contracts with the frontend engineers who consume them.

- Maintain the architecture decision record, lead design reviews, and support the legacy TypeScript service until it is retired.

Core Essentials

- 5+ years of professional backend engineering, including production ownership of a system you designed.

- Deep backend fundamentals in any language (Python, Go, Java, Kotlin, C#, TypeScript or Rust), and willingness to become effective in Python, FastAPI, and an asynchronous codebase.

- A strong instinct for concurrency hazards such as race conditions, lost updates, and messages processed twice.

- Strong PostgreSQL and SQL: data modelling, transactions and concurrency control, indexing, and migration practice.

- Experience with message queues and event-driven architecture, including idempotent retries, dead-lettering, and timeout handling, and with integrating external services designed for failure.

- Disciplined engineering practice (static typing, automated testing, code review, CI/CD, Docker) and productive use of AI coding assistants.

- Ability to work independently, set technical direction, and raise concerns about a requirement before implementing it; comfortable working in both Chinese and English.

Bonus Skills

- Hands-on Google Cloud Platform experience.

- Medical imaging experience, particularly DICOM and libraries such as pydicom, or a background in regulated healthcare software handling protected health information.

- Multi-tenant SaaS experience, especially database-enforced isolation such as row-level security, or products that also ship on-premise.

- Numerical or geometric computing (NumPy, computational geometry) and working familiarity with React and TypeScript.