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.