Backend Engineer, Expansion

What you'll do The Expansion pod brings creativity and executional rigor to attracting new prospects and driving conversion, focusing on user journeys, interactive and highly polished tools for users, and building targeted experiences for our global users. As a backend engineer, you'll architect and build the server-side systems and LLM orchestration layers that power intelligent, dynamic user experiences across acquisition journeys. You'll design the APIs, data pipelines, and inference infrastructure behind delightful and original interactive tools and resources that attract users. You'll collaborate deeply across design, engineering, and cross-functional teams and work across teams and tech stacks to create new site capabilities—with a specific focus on integrating large language models into production-grade services that are reliable, performant, and safe. This is not a research or ML training role. You'll be responsible for wiring LLMs into real user-facing products—managing prompt pipelines, handling model routing and fallback logic, and implementing guardrails and output validation. Responsibilities Develop and implement the tooling and platforms to support interactive content tools (e.g., calculators, generators, templates) that provide utility to current and prospective businesses Utilize a user-first mindset to implement feedback mechanisms for continuous improvement of content and product offerings Design and build integrations to third-party software and create seamless workflows across these tools to unleash their full potential to the rest of Stripe Ensure reliability, security, and responsible AI practices across all LLM-driven features, including implementing content filtering, PII handling, rate limiting, graceful degradation, and output guardrails Work with a small team of technically sophisticated engineers who put users first Who you are We're looking for someone who meets the minimum requirements to be considered for the role. If you meet these requirements, you are encouraged to apply. The preferred qualifications are a bonus, not a requirement. Minimum requirements 5+ years of backend development experience, with emphasis on building APIs and services that power user-facing experiences Experience writing clear, elegant code in a team environment Familiarity with LLM APIs and concepts—prompt engineering, token management, embedding models, retrieval-augmented generation, or function calling. You don't need to be a researcher, but you understand how these models work well enough to build production systems around them. Experience building and operating distributed backend systems—you're comfortable with service-oriented architectures, async processing, caching layers, and monitoring and alerting in production Passion for engineering solutions focused around growth hacking and enablement Excellent verbal and written communication Preferred qualifications Proven ability to stitch different services and processes together even if you haven't worked with them before Experience in developing interactive tools and integrating them with existing systems Experience building highly complex interactive tools, including state management and data fetching Experience with data pipeline orchestration (Airflow, Dagster, Temporal, or similar) and structured output parsing from LLMs Experience with prompt versioning, A/B testing model outputs, or building model gateway and routing layers that allow teams to swap or compare providers (e.g., OpenAI, Anthropic, open-source models) • Proficiency with React, with a focus on interactions, animation, performance, and polish • Experience with A/B testing, synthetic monitoring, or accessibility testing