Senior Python Backend Engineer – Real-Time Voice AI & LLMs

Phonely; San Francisco (CA); On-site; USD 140,000 - 190,000; Full time

Job summary

Phonely in San Francisco is seeking a Senior Backend Engineer (Python) to build and maintain stateful Python systems that drive the voice AI in real-time conversations. You will integrate multiple LLM providers, design robust APIs, and write high-performance code.

This role focuses on testing, reliability, and scalable architectures, with emphasis on security, metrics, and observability. Office-based 5 days a week in San Francisco offers a collaborative, fast-moving environment shaping

Qualifications

• 5+ years writing Python, experience writing async web apps using FastAPI, testing frameworks.
• Understanding of LLMs, APIs, cloud and CI/CD pipelines.
• Comfortable with technical specifications.
• Understanding of good architecture and security practices.
• Strong technical and communication skills.
• Experience with AWS and Kubernetes.

Responsibilities

• Build and maintain Python-based state systems that drive what the voice AI says and does across complex, real-time conversations.
• Integrate and orchestrate multiple LLM providers, including prompt design, tool/function calling, routing, and fallbacks.
• Write clean, maintainable, high-performance Python code, leveraging asyncio, OOP, and best practices.
• Write automated tests and validation suites to ensure correctness, resilience, and safe iteration of agent logic and state transitions.
• Monitor production systems, debug agent behavior, and continuously improve reliability and conversation quality.
• Implement comprehensive metrics, logging, and alerting to validate correctness, detect failures early, and maintain extremely high availability.
• Design database schemas, optimize queries, and operate both SQL and NoSQL databases in production.
• Build and operate authentication and authorization mechanisms with strong security guarantees.
• Design and build microservices-based architectures.

Skills

Python

Async web apps (FastAPI)

LLMs & APIs

CI/CD pipelines

Security & architecture

AWS

Kubernetes

Testing frameworks

Communication skills

Tools

FastAPI

Docker

Redis

Job description

Phonely in San Francisco is seeking a Senior Backend Engineer (Python) to build and maintain stateful Python systems that drive the voice AI in real-time conversations. You will integrate multiple LLM providers, design robust APIs, and write high-performance code.

This role focuses on testing, reliability, and scalable architectures, with emphasis on security, metrics, and observability. Office-based 5 days a week in San Francisco offers a collaborative, fast-moving environment shaping