Sr. Machine Learning Engineer

AppFolio Inc; Atlanta (GA); On-site; USD 167,000 - 230,000; Full time

Job summary

AppFolio is hiring a Senior Machine Learning Engineer to design and ship production voice and conversational AI agents in its Realm-X AI-native platform. Architect voice and text agent pipelines for real-time, multi-turn customer interactions while balancing reasoning depth and latency across LLMs and routing strategies.

Lead a small pod of ML and platform engineers; improve agent evaluation, observability, and incident response.

Qualifications

• 5+ years of experience building and scaling web-based apps, SaaS preferred.
• Shipped production AI agents for voice and/or text channels.
• Think in pipelines and systems, not only models.
• Strong engineering judgment and collaborative, low-ego attitude.
• Proven leadership of small teams and cross-functional partnerships.
• Experience with LangChain and related tooling for agent frameworks.

Responsibilities

• Architect and ship voice and text agent pipelines for real-time, multi-turn customer interactions.
• Balance reasoning depth vs. latency across frontier LLMs, smaller models, and routing strategies.
• Lead a small pod of ML and platform engineers; improve agent evaluation, observability, and incident response.
• Partner with Product and Voice teams to define KPIs, build eval harnesses, and establish acceptance criteria for agent quality.
• Drive selective fine-tuning and inference optimization to improve voice latency and cost.
• Apply agent and voice research to reliable, low-latency, multi-channel experiences at scale.

Skills

Python

LangChain

LangGraph

LangSmith

LangChain Deep Agents

Voice-to-Voice models

TTS / STT pipelines

LLM reasoning

Docker

AWS

Twilio

WebSockets

Async programming

Mentor engineers

Leadership

Education

Bachelor's degree in CS or related field

Master's or Ph.D. in CS (nice to have)

Tools

Docker

AWS

Job description

AppFolio is hiring a Senior Machine Learning Engineer to design and ship production voice and conversational AI agents in its Realm-X AI-native platform.

Responsibilities

• Architect and ship voice and text agent pipelines for real-time, multi-turn customer interactions.
• Make principled reasoning depth vs. latency trade-offs across frontier LLMs, smaller models, and routing strategies.
• Lead a small pod of ML and platform engineers; improve agent evaluation, observability, and incident response.
• Partner with Product and Voice channel teams to define KPIs, build eval harnesses, and establish acceptance criteria for agent quality.
• Drive selective Small Language Model (SLM) fine-tuning and inference optimization to improve voice latency and cost.
• Apply agent and voice research to reliable, low-latency, multi-channel experiences that scale across the customer base.

Requirements

• 5+ years of experience developing and scaling web-based applications, ideally in SaaS environments.
• Shipped production AI agents serving real users in voice and/or text channels.
• Think in pipelines and systems, not only models.
• Maintain strong engineering judgment.
• Demonstrate humble, collaborative, low-ego behaviors and elevate peers.
• Value work-life balance as a foundation for sustained high performance.
• Deep, shipped experience with LangChain, LangGraph, LangSmith, and LangChain Deep Agents (or equivalent agent frameworks).
• Hands-on with Voice-to-Voice models and traditional TTS / STT pipelines; understand trade-offs between end-to-end voice models and modular STT + LLM TTS architectures.
• Strong grasp of LLM reasoning behavior, tool use, structured output, and reasoning-vs-latency trade-offs across providers.
• Production experience with Twilio (or comparable telephony) and AWS.
• Expert Python, async programming, and WebSockets for real-time, bidirectional streaming.
• Solid foundation in deep learning, model evaluation, and inference optimization; deploy with Docker on AWS.
• Proven ability to lead a small team, mentor engineers and partner credibly with Product and Design.

Technologies

• Python, async programming, WebSockets
• LangChain, LangGraph, LangSmith, LangChain Deep Agents
• Voice-to-Voice models, TTS, STT
• LLM, Small Language Models (SLM)
• Twilio, AWS, Docker
• Real-time, bidirectional streaming

Nice to Have

• Bachelor's, Master's, or Ph.D. in Computer Science or related technical discipline.
• Experience fine-tuning Small Language Models for domain-specific voice applications.
• Familiarity with RAG over structured business data and tool-using agents over API surfaces.
• Prior experience in regulated or customer-facing industries with strict reliability requirements.
• Publicly verifiable work on GitHub, in open-source agent frameworks, or in community competitions.

Location

• Atlanta, GA (onsite)
• Find out more about locations by visiting the site.
• All late-stage candidates complete an in-person meeting with an AppFolian as part of the hiring process.

Compensation & Benefits

• Base pay: $167,200 - $229,900 per year
• Actual compensation depends on skills, education, experience, and internal equity.
• Regular full-time employees are eligible for benefits (see here).