Principal Machine Learning Engineer

AppFolio Inc is building the next generation of AI systems within Realm-X and is extending that work into an autonomous Real Estate Performance Management (RPM) platform. In this Principal Machine Learning Engineer role (onsite in Goleta, CA), you will help define mission-critical AI capabilities across architecture, agentic systems, and production machine learning excellence.

What you will do

• Define the technical vision and architecture for AI systems across Realm-X in partnership with senior leadership.
• Design and deploy advanced AI agentic systems that combine reasoning, planning, and execution, including multi-agent orchestration across specialist agents such as maintenance, leasing, accounting, and collections.
• Create platform primitives and abstractions that support context-aware, action-oriented AI for true automation beyond basic assistance.
• Raise end-to-end ML standards across data collection, model training, evaluation, deployment, and inference infrastructure.
• Architect and build scalable, multi-modal, real-time AI applications with high-quality deployment practices.
• Lead the transition toward autonomous property management operations using existing LLMs today, while instrumenting proprietary data collection to support selective training, fine-tuning, and RL optimization of open source LLMs and SLMs for the RPM domain, targeting performance, latency, and cost.
• Build data and feedback loops that enable reinforcement learning over agent action policies in a partially observable, high-stakes property management environment.

Requirements

• Master’s or Ph.D. in Computer Science, Machine Learning, or a related field (required).
• 10+ years of experience building software systems, with significant focus on ML/AI (or equivalent impact).
• Published research and shipped production systems.
• Working knowledge of traditional machine learning, deep learning, and generative AI / LLMs including prompting, fine-tuning, RAG, agents, and tool and skills use.
• Direct hands-on experience with LLM post-training at non-trivial scale, including SFT, RLHF, DPO, and/or RL.
• Strong understanding of data extraction, model training, evaluation, deployment, and integration into production software.
• Expertise with Python, PyTorch, NumPy, AWS, Docker, SQL, embeddings, and RAG.
• Experience with LangChain, LangGraph, and LLM observability tools such as LangSmith.
• Experience designing and operating production-grade ML systems at scale.
• Applied experience with ontology-driven systems, knowledge graphs, or semantic layers used to model business domains for AI systems.
• Proficiency with AI coding tools and workflows, such as Copilot and ChatGPT, and code generation tools.

Technologies

• Python, PyTorch, NumPy
• AWS, Docker, SQL
• Embeddings, RAG
• LangChain, LangGraph, LangSmith
• Copilot, ChatGPT
• SFT, RLHF, DPO
• LLMs, SLMs

Benefits

• Regular full-time employees are eligible for benefits.
• Compensation range: $264,000 - $363,000 base pay.
• Additional benefits or discretionary bonuses may be eligible based on role and/or employment type.

Nice to have

• Deep RL expertise applied to sequential decision-making under partial observability.
• Experience designing evaluation and benchmarking systems for AI.
• Background in distributed systems and real-time architectures.
• Experience building platforms used by multiple engineering teams.
• Contributions to industry thought leadership such as publications, talks, and open source.

Location and interview process

The role is based in Goleta, CA (onsite). Late-stage candidates complete an in-person meeting with an AppFolio team member as part of the hiring process.

Education: Master’s or Ph.D. in Computer Science, Machine Learning, or related field. Experience: 10+ years. Compensation: $264,000 to $363,000 per year base pay.