Sr. Machine Learning Engineer

AppFolio is hiring a Senior Machine Learning Engineer to design and ship voice and conversational AI agents for its Realm-X platform. The role builds production voice and text agent pipelines, balancing reasoning quality, latency, and cost while partnering with Product, Voice channel, and ML Platform teams.

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

Requirements:

• You have 5+ years of experience developing and scaling web-based applications, preferably in a SaaS environment
• You have shipped production AI agents serving real users in voice and/or text channels
• 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; understands the 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; able to deploy with Docker on AWS
• Demonstrated ability to lead a small team, mentor engineers, and partner credibly with Product and Design
• 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