Founding Engineer

About Kastle

Kastle is building the AI operating system for consumer lending. We partner with some of America’s largest mortgage lenders to transform their contact centers and compliance operations with AI voice agents.

Backed by $2.3M from Y Combinator, Commerce Ventures, and executives from Snapdocs, Google, and WePay, we’re redefining how millions of borrowers interact with financial institutions and how lenders operate at scale.

This is a rare chance to join at the ground floor of a company already plugged into large-scale customers and real production use cases.

What You’ll Do

• Architect and own core systems that power real-time AI voice and compliance workflows

• Push performance boundaries, delivering sub-700ms latency leveraging event driven architecture and parallel processing

• Deploy, operate, scale, resilient systems using Kubernetes and distributed sub-systems

• Build a self-improving AI system that improves with every customer interaction and human feedback

• Ship fast, ship right from whiteboard design to live production in bank environments.

Why Join Kastle?

• Build what banks run on: Your code won’t sit in a sandbox, it’ll power real borrower interactions at scale.

• Act like a founder: High ownership, autonomy, and input on product, tech, and culture.

• Learn fast: Daily exposure to customers and their feedback loops.

• Strong upside: Competitive salary, meaningful early-stage equity, and a front-row seat to building a category-defining company.

• Great team: Work side-by-side with a world-class founding team from Verkada, NVIDIA, Apple, and Redfin.

What You Bring

• Strong fundamentals in building high-performance, real-time backend systems (we work primarily in Python).

• Deep understanding of distributed systems, reliability, and fault tolerance.

• Excellent database design and performance optimization skills.

• A bias for ownership and an ability to figure things out in messy, high-velocity environments

Nice to Have

• Experience with training, designing, or building production AI/ML systems

• Previous startup or founder experience.

The Interview Process

We respect your time. Our process is short and designed to let you showcase how you think:

1. 15-min call with CEO

2. 1-hour live coding session with CTO

3. 1-day onsite with team