# Senior Backend Engineer

**Company:** [Phonely](https://hotfix.jobs/companies/phonely)
**Location:** San Francisco, CA
**Role:** Backend Engineering
**Salary:** $200k – $350k/yr
**Experience:** 5+ years
**Skills:** Python, FastAPI, Asyncio, Kubernetes, AWS, GCP, Redis, SQL, NoSQL, LLMs, Datadog, CI/CD, Microservices, Firebase, Supabase
**Posted:** 2026-04-09

> Builds and maintains Python-based state systems and microservices for real-time voice AI agents, integrating LLMs and ensuring high availability. Requires 5+ years Python experience with async web apps, FastAPI, AWS, and Kubernetes.

## Job Description

## 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.

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

## Software Stack
- **Backend**: Python, microservices, async programming.
- **Cloud & Infrastructure**: AWS, GCP, Kubernetes, Redis.
- **Databases**: Firebase, Supabase.
- **Observability & Monitoring**: Datadog, logging, metrics, tracing.
- **Telephony & Voice AI**: SIP, voice APIs, real-time call handling.
- **Other tools & practices**: CI/CD, automated testing, resilient architecture.

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**Apply:** https://hotfix.jobs/jobs/103aece1-2b9b-480b-b2c3-4c3ee37adcdd
**Canonical:** https://hotfix.jobs/jobs/103aece1-2b9b-480b-b2c3-4c3ee37adcdd