Senior Backend Engineer

About the Position

We are looking for a Senior BackendEngineer to design, develop, and maintain backend services and AI-poweredapplications. You will deliver new features, integrate AI capabilities, andimprove the reliability, performance, and maintainability of existing systems.

This is a senior, hands-on individualcontributor role. You will write code, contribute to architectural decisions,and collaborate with cross-functional teams to turn product requirements andemerging AI capabilities into production-ready solutions.

Responsibilities

Backend Development and Maintenance

· Build and maintain scalablePython services and secure RESTful APIs using FastAPI.

· Own features from technicaldesign and implementation through testing, deployment, and ongoing support.

· Extend existing applications,troubleshoot production issues, refactor code, and manage dependency upgradeswhile preserving API compatibility.

· Design and optimize databaseaccess, caching, and asynchronous processing.

· Implement authentication,authorization, input validation, and reliable error handling.

AI Application Development

· Integrate LLMs and other AIservices through provider APIs and SDKs, creating reusable interfaces forapplication teams.

· Design reliable APIs and toolinterfaces for AI applications, with well-defined input/output schemas,validation, and error handling.

· Develop AI workflows usingprompt orchestration, structured outputs, tool calling, and streamingresponses.

· Manage context limits, ratelimits, timeouts, retries, and provider failures to support reliable productionuse.

· Evaluate model and promptchanges against representative test cases, balancing output quality, latency,and cost.

· Design and develop multi-agentsystems and workflows, where appropriate, to address business requirements andautomate complex tasks.

Quality Delivery and Collaboration

· Write automated tests andmaintain regression coverage for backend services and AI integrations.

· Improve logging, metrics, andtracing to diagnose failures and monitor service performance and AI usage.

· Maintain CI/CD pipelines andcontainerized deployments in collaboration with infrastructure teams.

· Conduct code reviews, documenttechnical decisions, and mentor junior engineers.

· Partner with product, frontend,AI, and infrastructure teams to clarify requirements and deliver maintainablesolutions.

Must Have

· 5+ years of professional backend development experience, including2+ years developing AI-powered applications or services, with demonstrated ownership of service design, productiondeployment, and ongoing maintenance.

· Strong Python and FastAPI expertise,including asynchronous programming, type annotations, Pydantic, dependencyinjection, and RESTful API design.

· Practical experienceintegrating AI APIs or SDKs, including prompt design, structured outputs, andstreaming or asynchronous workflows.

· Understanding of common LLMchallenges, including context management, hallucinations, prompt injection,rate limits, and token costs.

· Hands-on public cloud experience, suchas AWS, Azure, or GCP, including deploying and operating backend applications.

· Solid database skills withPostgreSQL or another relational database, including data modeling and queryoptimization.

· Working knowledge of secure APIdesign, authentication and authorization, and secrets management.

· Experience designing reliablebackend services and external API integrations, including concurrency control,timeouts, retries, idempotency, and rate limiting, with the ability to explaindesign tradeoffs.

· Experience with pytest orequivalent testing tools, Git, CI/CD, and Docker.

· Strong problem-solving skillsand the ability to independently navigate, extend, and improve an existingcodebase.

· Strong written and verbal communication skills in both English andChinese, with the ability to explain technicaldecisions and tradeoffs across teams.

Nice to Have

· AWS experience, particularly with S3,SageMaker, DynamoDB, ECS, CloudWatch, or Secrets Manager.

· Frontend development experience with Vue or React, including TypeScript or JavaScript.

· Experience with agentframeworks such as LangGraph, Pydantic AI, Claude Agent SDK, or comparabletools, including multi-agent orchestration, task delegation, and contextsharing.

· Experience withretrieval-augmented generation (RAG), embeddings, and vector databases such aspgvector.

· Experience deploying local orself-hosted LLMs using tools such as vLLM, Ollama, or llama.cpp.

· Experience with multimodal AI,including image, audio, or 3D generation.