Sr. Machine Learning Engineer

AppFolio is hiring a Sr. Machine Learning Engineer in Columbus, OH to help design and deliver voice and conversational AI agent pipelines within Realm-X. The role centers on low-latency, multi-channel experiences that combine LLM agent frameworks, real-time voice capabilities, and streaming infrastructure.

What you will do

• Architect and ship voice and text agent pipelines for real-time, multi-turn customer conversations.
• Make well-reasoned trade-offs between reasoning depth and latency across frontier LLMs, smaller models, and routing strategies.
• Lead a small pod of ML and platform engineers, raising the bar across agent evaluation, observability, and incident response.
• Work with Product and Voice channel teams to define KPIs, build evaluation harnesses, and establish agent quality acceptance criteria.
• Drive selective Small Language Model (SLM) fine-tuning and inference optimization to improve voice latency and reduce cost.

What you bring

• Deep, shipped experience with LangChain, LangGraph, LangSmith, and LangChain Deep Agents (or equivalent agent frameworks).
• Hands-on experience with Voice-to-Voice models and traditional TTS/STT pipelines, including understanding the trade-offs between end-to-end voice models and modular STT LLM TTS architectures.
• Strong understanding 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, including deployment with Docker on AWS.
• Proven ability to lead a small team, mentor engineers, and partner effectively with Product and Design.
• Experience shipping production AI agents serving real users in voice and/or text channels.
• Systems-oriented thinking (pipelines and architecture, not only models) plus fast execution with sound engineering judgment.
• Collaborative, low-ego approach that elevates others, with an emphasis on sustainable work-life balance.

Technologies

• LangChain, LangGraph, LangSmith, LangChain Deep Agents
• Voice-to-Voice models, TTS, STT
• Twilio, AWS
• Python, WebSockets
• Docker

Nice to have

• 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, open-source agent frameworks, or in community competitions.

Location

Columbus, OH (onsite).

Find out more about locations by visiting the company site. All late-stage candidates complete an in-person meeting with an AppFolian as part of the hiring process.

Compensation & benefits

• Salary range: USD 167,200 - 209,000 per year (base pay).
• The actual compensation will be determined by factors including skills, education, experience, and internal equity.
• Regular full-time employees are eligible for benefits.

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