Founding Engineer at Kastle (S24)

Kastle | San Francisco, California, United States | 1w ago

skills: python, asyncio, fastapi, django, kafka, rabbitmq, redis streams, postgresql, nosql, kubernetes, llm engineering, backend development, api design, event-driven architecture

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Founding Engineer at Kastle

About Kastle

Kastle is building AI operating system 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 using AI voice agents. Backed by $2.3M from Y Combinator, Commerce Ventures, and executives from Snapdocs, Google, and WePay, we are redefining lending with AI.

About the Role

We’re looking for a Founding Engineer to build and optimize the Kastle platform. As an early team member, you’ll have a pivotal role in architecting and scaling our AI systems, ensuring high availability, low latency, and compliance with strict financial regulations.

You’ll work closely with the founding team to design, develop, and deploy mission-critical AI applications that integrate with financial institutions. This role requires expertise in backend development and LLM Engineering—ideal for an engineer who thrives in high-impact environments.

Responsibilities

Architect and develop scalable backend services for AI-driven consumer lending applications.
Design and implement APIs that integrate with loan servicing platforms, payment processors, and compliance systems.
Optimize performance for real-time AI interactions, ensuring sub-700ms latency.
Manage containerized deployments using Kubernetes to maintain high availability and reliability.
Develop event-driven architectures using Python AsyncIO for parallel processing and real-time automation.
Own the full development lifecycle—from designing scalable solutions to deploying and monitoring them in production.

Minimum Requirements

1+ years of backend engineering experience in high-velocity environments.
Expertise in Python, with strong knowledge of AsyncIO, FastAPI, or Django.
Familiarity with event-driven architectures and message queues (e.g., Kafka, RabbitMQ, or Redis Streams).
Strong database skills, including PostgreSQL or other relational/NoSQL databases.
Excellent problem-solving skills and a passion for optimizing backend performance.

Preferred Qualifications

Background in AI/ML-powered systems, especially LLM applications.
Previous startup experience, with a hands-on approach to problem-solving.

Why Join Kastle?

Build the AI operating system that large banks and lenders run on.
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.

Benefits

early-stage equity · company paid site visits

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