Founding Applied AI Engineer at Kastle

Kastle (YC S24); San Francisco (CA); On-site; USD 110,000 - 150,000; Full time

Benefits offered by this job

Competitive salary

Early-stage equity

Frequent company paid visits to customers

Job summary

Kastle (YC S24) is looking for a Founding Applied AI Engineer in San Francisco to integrate cutting-edge AI technologies into their platform. You will fine-tune large language models and design AI workflows that comply with mortgage servicing regulations.

The ideal candidate should have at least 1 year of experience in applied AI or ML engineering, and proficiency in Python and deep learning frameworks. This role offers competitive salary and equity, amidst a high-ownership environment.

Qualifications

• 1+ years in applied AI or ML engineering.
• Experience in fine-tuning large language models.
• Strong communication skills to collaborate with teams.

Responsibilities

• Fine-tune and deploy LLMs for real-time interactions.
• Design, test, and optimize AI prompts.
• Ensure AI compliance with regulatory standards.
• Build robust AI-driven workflows.

Skills

Applied AI

Machine Learning Engineering

Python

TensorFlow

PyTorch

Tools

Deep Learning Frameworks

Job description

About Kastle

Kastle is building AI agents for consumer lending starting with mortgage. We work with some of America’s largest mortgage lenders, helping them scale their contact center and compliance operations efficiently using AI-driven voice agents. Backed by $2.3M from Y Combinator, Commerce Ventures, and executives from Snapdocs, Google, and WePay, we are redefining loan servicing with AI.

About The Role

As a Founding Applied AI Engineer, you will play a crucial role in integrating advanced AI technologies into Kastle’s platform. You’ll work on fine-tuning large language models (LLMs), designing AI workflows for highly regulated enterprises, and ensuring our AI agents deliver precise, compliant, and effective interactions. This role is ideal for an engineer who is passionate about applied AI, eager to solve real-world challenges, and excited to build the technical foundation of an early-stage AI startup.

Responsibilities

• AI Model Integration: Fine-tune and deploy LLMs for real-time borrower interactions.
• Prompt Engineering: Design, test, and iterate on prompts to optimize AI performance and compliance.
• Custom AI Solutions: Train and implement domain‑specific AI models for mortgage servicing.
• Scalability & Compliance: Ensure AI solutions meet regulatory standards (FDCPA, RESPA, TILA) and scale efficiently.
• Data Pipelines & APIs: Build robust AI‑driven workflows that integrate seamlessly with loan servicing platforms.
• Continuous Optimization: Monitor AI performance, reduce error rates, and enhance borrower experience.

What We’re Looking For

• 1+ years in applied AI, ML engineering, or a related role.
• Proficiency in Python, TensorFlow/PyTorch, and deep learning frameworks.
• Experience fine‑tuning LLMs (Llama, GPT) and designing AI prompt workflows.
• Strong product mindset—ability to bridge AI capabilities with real‑world mortgage servicing needs.
• Experience with deploying AI models into production and optimizing for speed and accuracy.
• Strong communication skills to collaborate with product, engineering, and compliance teams.

Why Join Kastle?

• Build and scale AI applications that interface directly with consumers.
• Get to interact directly with customers on a daily basis and see them use your work in production and collect feedback.
• Work closely with a world‑class founding team backed by top investors.
• High ownership and autonomy, shaping the company’s technical direction.
• Competitive salary, early‑stage equity, and frequent company paid site visits to customers.