About the position
We’re looking for a Senior Backend Engineer to join our newly formed AI R&D pod—a small, fast-moving team dedicated to building the future of AI-native product experiences at Posh. This is a backend-focused role with a strong emphasis on systems architecture and AI implementation. You will be responsible for building the intelligent, scalable, and reliable systems that power our AI features. Your work will focus on designing and deploying sophisticated Multi-Agent Systems, moving beyond simple RAG to create truly autonomous and helpful user experiences. You’ll work closely with frontend engineers and product designers to bring cutting-edge AI tools to our platform. Expect to build robust APIs, architect data flows for evaluations and fine-tuning, and pioneer new ways to leverage AI within our existing infrastructure. This represents a unique opportunity to build the foundational backend of our AI products, with the chance to ship experimental features to a large, growing, and highly engaged user base.
Responsibilities
- Design, build, and maintain scalable backend services and APIs for AI-powered features, writing primary production code in Python.
- Move beyond standard RAG to design and implement complex, hierarchical Multi-Agent Systems that can perform sophisticated, multi-step tasks.
- Build robust frameworks to evaluate the quality of AI systems and manage fine-tuning pipelines to continuously improve model performance.
- Define, deploy, and manage our AI infrastructure using Terraform.
- Scale our container-based serverless solutions while ensuring reliability and performance.
- Analyze the tradeoffs between model performance, latency, and cost to make pragmatic, business-aware technical decisions when using managed AI services.
- Collaborate with core engineering teams by occasionally working in TypeScript (Node.js) to integrate AI features into our main application.
Requirements
- 3–6+ years of backend or full-stack engineering experience, with a proven track record of shipping high-quality, scalable systems in fast-paced environments.
- Deep expertise in Python and its ecosystem for web services and data processing.
- Strong experience with Infrastructure as Code (Terraform), a major cloud platform (e.g., GCP, AWS, Azure), and deploying containerized applications.
- Hands-on experience using managed AI services (e.g., Vertex AI, AWS Bedrock), working with LLMs, and building advanced AI systems.
- Experience with model evaluation frameworks (e.g., RAGAs, LangSmith, DeepEval) and fine-tuning is highly desired.
- Strong ability to evaluate the tradeoffs between cost, latency, and performance is essential.
Nice-to-haves
- Experience with open-source agentic frameworks (e.g., LangGraph, CrewAI, Strands, etc).
- A passion for shaping 0→1 products in a lean, fast-paced R&D environment.
- Bonus points for experience with MLOps, data engineering, or a background in consumer, marketplace, or event-driven platforms.
