Senior/Staff Software Engineer (Full-Stack Engineer)

About Actively AI Actively AI is defining a new category: Intelligence-Led Revenue. Revenue organizations have always been bottlenecked on human capacity. Reps triage which accounts get attention. Context disappears at every handoff. On any given day, the vast majority of accounts have exactly zero people thinking about them. Actively addresses this at the structural level. Our platform deploys Per-Account AgentsTM across our customers’ TAM, working 24/7 to research, identify opportunities, and advance next steps without being asked. Leading enterprises including Ramp, Ironclad, and Samsara are already making this shift. Our co-founders are former Stanford AI researchers, and the team comes from Harvard, CMU, Berkeley, Brex, Scale AI, and Google. We've raised $68M from TCV, First Harmonic, Bain Capital Ventures, First Round Capital, and more. About the Role We’re looking for a Senior/Staff Full Stack Engineer to architect and build the foundational systems that define how users interact with Actively’s AI Agents through web interface as well as real-time workflows enabled via Chat. For most of Actively's history, our intelligence has run quietly in the background, wired into Salesforce, Outreach, and the tools your customers already use. We're now building the product itself: the surface where users actually see what agents are doing, give direction, and collaborate in real time. This is a foundational role. You'll own the core product experiences that define how Actively feels, from Python/FastAPI backends and workflows to the React/TypeScript interfaces that bring them to life. You'll establish the design patterns, platform architecture, and technical standards that every future surface is built on top of. You'll prototype new agent interactions, run experiments, and work directly with customers to make complex AI behavior feel natural and trustworthy. For more on how we think about human-agent collaboration, see our blog post . What You’ll Do Own end-to-end features. Design, build, and ship customer-facing experiences across the stack, from Python/FastAPI services and background workers to polished React/TypeScript UIs. Define Actively’s product platform. Architect the frameworks, patterns, and shared product components that make every product surface fast, consistent, and cohesive. Design and prototype intelligent AI interactions. Collaborate with agent SDKs and internal frameworks to build new user experiences for configuring, debugging, and collaborating with agents including conversational interfaces, feedback loops, and workflow builders. Build for real usage at scale. Operate across the full stack to ensure high performance, reliability, and seamless data flow, working across SQL/NoSQL stores, caching layers, and task execution pipelines, and contributing to backend systems where needed to deliver a cohesive end-to-end experience. Customer-driven iteration. Work directly with customers and alongside other teams to translate real feedback and behavior into simple, easy-to-use experiences, experimenting and refining quickly based on what customers actually need. Who You Are A seasoned, product-minded engineer. You have 5+ years of experience building and shipping high-impact, customer-facing products end-to-end — from backend APIs to refined UI experiences. Product-minded and design-curious . You care about usability, polish, and the emotional feel of software as much as the systems behind it. Frontend-strong, backend-capable . You have deep experience with React, TypeScript, and modern web frameworks, and you’re comfortable working in Python/FastAPI backends to craft seamless full-stack flows. A systems thinker. You recognize the patterns behind good architecture and design frameworks that help others move faster without sacrificing quality. You think in terms of type safety, API contracts, and shared platform primitives. Iterative by nature. You thrive in fast feedback loops; building, learning, and refining quickly b