Senior Software Engineer, Backend (AI)

ABOUT POSH We are all social creatures, but the dominant “social” companies today have evolved into digital loneliness machines, driving isolation, anxiety, and mental health challenges around the world. Human connection is lost. Posh is a beacon guiding us back. Posh enables anyone to build an IRL community based on shared interests, while connecting consumers with the communities of people just like them. Founded by event organizers who were frustrated with the growing loneliness epidemic and the tools available to build their own event brand, we’ve built the ultimate platform for launching, monetizing, and finding IRL communities of people just like you. In just 6 years, Posh has grown to a team of 70, expanded to 8M+ users, secured $70m in venture funding, and facilitated over $350M in transactions. ABOUT THE ROLE We're looking for a Senior Backend Engineer to join our AI Platform team, a small, fast-moving group building the backend infrastructure that powers AI-native product experiences at Posh. This is a backend systems and infrastructure role. You'll design, build, and scale the services, APIs, and cloud infrastructure that our AI features run on. You won't be training models. You'll be building the reliable, performant platform that makes our AI products work in production. Your work will include architecting data flows, building evaluation pipelines, deploying containerized services, and integrating AI capabilities into our core product. You'll collaborate closely with frontend engineers and product managers to ship experimental features to a large, highly engaged user base. WHAT YOU'LL DO - Design and Scale Backend Services: Build and maintain scalable backend services and APIs that power AI-driven features, writing production code primarily in Java, and Python. - Own Cloud Infrastructure: Define, deploy, and manage AI infrastructure using Terraform on a major cloud platform (AWS). Scale container-based solutions while ensuring reliability and performance. - Build Evaluation Pipelines: Create robust frameworks to evaluate AI system quality and continuously improve model performance. - Optimize for Cost, Latency, and Performance: Make pragmatic, business-aware decisions about the tradeoffs between model quality, response time, and infrastructure cost when working with managed AI services. - Integrate Across the Stack: Collaborate with core engineering by occasionally working in TypeScript (Node.js) to connect AI features into Posh's main application. - Support Agent Architecture: Build the backend systems and data flows that power our multi-step, autonomous AI workflows, ensuring they are reliable, observable, and scalable. WHAT WE'RE LOOKING FOR - 3 to 6+ years of backend or full-stack engineering experience, with a 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 (GCP, AWS, or Azure), and deploying containerized applications. - Comfort operating in a 0→1 environment where you'll help define new patterns and practices for AI-native product development. BONUS POINTS - Experience with managed AI services (Vertex AI, AWS Bedrock, etc.), working with LLMs in production, or building evaluation frameworks (RAGAs, LangSmith, DeepEval). - Familiarity with agentic frameworks (LangGraph, CrewAI, Strands) or multi-agent system design. - Background in MLOps, data engineering, or experience at consumer, marketplace, or event-driven platforms. WHY THIS ROLE MATTERS We believe AI will reshape how people plan and participate in real-world experiences. The companies that integrate AI directly into their product to create visible, daily value will define the next generation of consumer software. At Posh, we're not building infrastructure for others. We're leading our category with a product that feels intelligent, personal, and effort