Senior ML Engineer, Voice & AI Agents (Realm-X)

AppFolio; San Francisco (CA); Hybrid; USD 167,000 - 209,000; Full time

Job summary

AppFolio in San Francisco is hiring a Senior Machine Learning Engineer to design and ship the next generation of voice and conversational AI agents within Realm-X. You’ll help define production voice and chat agent pipelines, working at the intersection of LLM agent frameworks, real-time voice tech, and streaming infrastructure.

You will work with Product, Voice channel, and ML Platform teams to translate cutting-edge agent research into reliable, low-latency, multi-channel experiences that

Qualifications

• Agent frameworks: Deep, shipped experience with LangChain, LangGraph, LangSmith, and LangChain Deep Agents (or equivalent).
• Voice stack: Hands-on with Voice-to-Voice models and traditional TTS / STT pipelines; understands trade-offs between end-to-end voice models and modular architectures.
• LLM fluency: Strong grasp of LLM reasoning behavior, tool use, structured output, and latency trade-offs across providers.
• Telephony & cloud: Production experience with Twilio (or comparable telephony) and AWS.
• Engineering: Expert Python, async programming, and WebSockets for real-time, bidirectional streaming.
• ML fundamentals: Solid foundation in deep learning, model evaluation, and inference optimization; able to deploy with Docker on AWS.
• Leadership: Demonstrated ability to lead a small team, mentor engineers, and partner credibly with Product and Design.

Responsibilities

• Ship Voice & Text Agents: Architect and ship voice and text agent pipelines that handle real-time, multi-turn customer interactions.
• Reasoning vs. Latency: Make principled trade-offs between reasoning depth and latency across frontier LLMs, smaller models, and routing strategies.
• Lead a Pod: Lead a small pod of ML and platform engineers; raise the bar on agent evaluation, observability, and incident response.
• Define Quality: Partner with Product and Voice channel teams to define KPIs, eval harnesses, and acceptance criteria for agent quality.
• Optimize for Voice: Drive selective Small Language Model (SLM) fine-tuning and inference optimization for voice latency and cost.

Skills

Agent frameworks

Voice stack

LLM fluency

Telephony & cloud

Python & WebSockets

Docker & AWS

Leadership

Tools

Twilio

AWS

Docker

Python

WebSockets

LangChain

LangSmith

LangGraph

LangChain Deep Agents

Job description

AppFolio in San Francisco is hiring a Senior Machine Learning Engineer to design and ship the next generation of voice and conversational AI agents within Realm-X. You’ll help define production voice and chat agent pipelines, working at the intersection of LLM agent frameworks, real-time voice tech, and streaming infrastructure.

You will work with Product, Voice channel, and ML Platform teams to translate cutting-edge agent research into reliable, low-latency, multi-channel experiences that