Senior/Staff Software Engineer (Full-Stack Engineer)

Actively AI is building superintelligence for GTM teams, focused on increasing productivity for outbound teams. They are seeking a Senior/Staff Full Stack Engineer to architect and build foundational systems for user interaction with their AI Agents through web interfaces and real-time workflows.

Responsibilities:

• 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

Requirements:

• 5+ years of experience building and shipping high-impact, customer-facing products end-to-end — from backend APIs to refined UI experiences
• Deep experience with React, TypeScript, and modern web frameworks
• Comfortable working in Python/FastAPI backends to craft seamless full-stack flows
• Recognize the patterns behind good architecture and design frameworks that help others move faster without sacrificing quality
• Think in terms of type safety, API contracts, and shared platform primitives
• Thrive in fast feedback loops; building, learning, and refining quickly based on real-world use and customer insight
• Thrive in environments where the path isn't fully defined — making architectural and product calls without waiting for direction, owning outcomes end-to-end, and bringing structure to ambiguity
• Have shipped real AI-powered products and not just prototypes and know how to turn LLM capabilities into fast, trustworthy, user-facing experiences
• Track record of building 0→1 products in fast-moving, resource-constrained environments
• Experience as an early or founding engineer, where you owned architecture, product calls, and shipping and not just execution
• Deep experience building agentic UI systems, such as chat interfaces, agent inboxes, or task orchestration UIs