Staff Engineer

Kastle; San Francisco (CA); On-site; USD 120,000 - 150,000; Full time

Benefits offered by this job

Competitive salary

Meaningful early-stage equity

Exposure to customer feedback

Work with a world-class founding team

Job summary

Kastle is seeking a talented engineer to architect and own core systems for AI voice operations in San Francisco. In this role, you will have substantial ownership over your work and will tackle challenges to build high-performance, real-time systems primarily in Python. You will join a mission-driven team backed by top investors, pushing boundaries in a dynamic environment with meaningful early-stage equity. Join us to redefine consumer lending interactions.

Qualifications

• Strong fundamentals in building high-performance, real-time backend systems.
• Deep understanding of distributed systems, reliability, and fault tolerance.
• Excellent database design and performance optimization skills.
• Ability to operate in messy, high-velocity environments.

Responsibilities

• Architect and own core systems that power real-time AI voice and compliance workflows.
• Push performance boundaries for sub-700ms latency.
• Deploy and scale resilient systems using Kubernetes.
• Build a self-improving AI system.
• Ship fast from design to live production.

Skills

High-performance backend systems

Distributed systems

Database design and performance optimization

Ownership and problem-solving in dynamic environments

Tools

Python

Kubernetes

Job description

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 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.