Full Stack Engineer

SENIOR FULL STACK ENGINEER (REACT / NEXT.JS) At some point in the future, every business will answer their phone with voice AI. We are making sure that when they build that AI agent, the experience of doing so doesn’t suck. We’re growing incredibly fast and need someone who thrives in a dynamic, high-pressure environment to work across our engineering stack. This role is critical to the success of our company. We’re looking for someone who will roll up their sleeves, dig in, and double down when things get tough. We want someone highly technical, driven, and fun to work with. You’ll be working directly with engineering, product, and customer-facing teams to build and ship fast. NOTE: This is an engineering position. You will be writing a lot of code, and it will be a lot of work. If you’re looking for a cushy corporate job where nothing gets done, this is not the place. If you want to be part of a winning team and make a real difference, read on. This role is in-office 5 days a week in San Francisco. YOUR DAY-TO-DAY - Build and maintain high-performance, responsive web applications using React and Next.js - Design and implement end-to-end features across frontend and backend systems - Work closely with backend engineers to integrate APIs, real-time systems, and voice AI workflows - Own UI/UX quality—craft fast, intuitive, and reliable user experiences - Manage state effectively across complex applications (server + client state) - Optimize frontend performance (latency, rendering, caching, edge delivery) - Build internal tools and dashboards for monitoring, debugging, and controlling AI agents - Write clean, maintainable, and well-tested code across the stack - Debug production issues and continuously improve reliability and usability - Contribute to system design, architecture decisions, and product direction QUALIFICATIONS - 5+ years of experience building production applications - Strong experience with React and Next.js - Experience building full-stack applications (API design, backend integration) - Solid understanding of TypeScript, modern frontend tooling, and state management - Experience working with APIs, real-time systems, and async data flows - Understanding of performance optimization and scalable frontend architecture - Familiarity with cloud environments, CI/CD, and modern deployment workflows - Strong product sense and attention to detail - Clear communicator who can work across teams OUR SOFTWARE STACK - Frontend: React, Next.js, TypeScript - Backend: Python, microservices, async systems - Cloud & Infra: AWS, GCP, Kubernetes, Redis - Databases: Firebase, Supabase - Observability: Datadog, logging, metrics, tracing - Voice AI: SIP, real-time call handling, LLM orchestration - Other: CI/CD, testing, resilient architecture WHY JOIN PHONELY? We’re a team of ex-athletes, founders, and builders. Low ego, high standards. We believe life isn’t about taking the easy road - it’s about pushing yourself to see what you’re capable of. Working here feels like a team: - We eat meals together (company-paid) - We run, hike, and surf - We travel together (Airbnbs in places like the Rockies, Costa Rica, Indonesia—multiple times a year) We are deeply customer-obsessed and focused on building something we actually want to use. We’re tackling voice AI problems that haven’t been solved before, with a goal of building something 1M+ businesses love.