Senior Backend Engineer (Python)

Phonely | Senior Backend Engineer (Python) | San Francisco (Onsite) | Full-time We’re building the future of voice AI for businesses, with a platform designed to make real-time agents easy to build, tune, and operate. We’re looking for a senior backend engineer to work on core systems that drive live voice conversations in production. This is a hands-on role with a lot of ownership and a lot of Python. What you’ll do • Build Python-based state systems for real-time voice AI conversations • Integrate multiple LLM providers (prompting, routing, tool calling, fallbacks) • Write high-performance async Python (FastAPI, asyncio) • Design and test resilient agent logic and microservices • Operate and improve production systems with strong observability What we’re looking for • 5+ years of Python experience, including async web services • Experience with FastAPI, testing, and CI/CD • Strong system design and security fundamentals • Familiarity with LLMs, cloud infrastructure, AWS, and Kubernetes Stack Python, FastAPI, async microservices, AWS/GCP, Kubernetes, Redis, Firebase, Supabase, Datadog, SIP/voice APIs Why Phonely Small, intense team of builders. High ownership, fast pace, real impact. In-office 5 days/week in SF. Company-paid meals, great culture and periodic international work trips. https://www.ycombinator.com/companies/phonely/jobs/gp1xSAu-s...