Sr. Machine Learning Engineer

AppFolio is hiring a Senior Machine Learning Engineer in Atlanta, GA (onsite) to design and ship voice and conversational AI agents within Realm-X. In this role, you will build production agent pipelines and focus on practical delivery: balancing LLM reasoning with low-latency streaming across multi-channel customer experiences.

This position is a strong fit if you enjoy turning agent concepts into reliable systems, partnering with Voice and Product teams on measurable quality, and iterating quickly while maintaining sound engineering judgment.

What you’ll do

• Architect and ship voice and text agent pipelines for real-time, multi-turn customer interactions.
• Make principled 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 on agent evaluation, observability, and incident response.
• Partner with Product and Voice channel teams to define KPIs, build evaluation harnesses, and set acceptance criteria for agent quality.
• Drive selective SLM fine-tuning and inference optimization to improve voice latency and cost.

What you’ll 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 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; ability to deploy with Docker on AWS.
• Demonstrated ability to lead a small team, mentor engineers, and partner credibly with Product and Design.
• Experience shipping production AI agents serving real users in voice and/or text channels.
• Systems thinking, fast execution with impact, and strong engineering judgment; ability to collaborate with a low-ego, humble, and inclusive approach.
• Values work-life balance as a foundation for sustained high performance.

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

Technologies you’ll use

• LangChain, LangGraph, LangSmith, LangChain Deep Agents
• Voice-to-Voice models, TTS, STT
• Twilio, AWS, Python, async programming, WebSockets, Docker
• LLM, Small Language Model (SLM), RAG

Compensation & benefits

Base pay: USD 167,200 - 209,000 per year.

The actual compensation will be determined by factors including skills, education, experience, and internal equity. Compensation is part of a broader Total Rewards package and the range listed does not include additional benefits or any discretionary bonuses.

Regular full-time employees are eligible for benefits.

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