Sr. Machine Learning Engineer

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).