Founding Backend Engineer at Kastle (S24)

Founding Backend Engineer at Kastle

About Kastle

Kastle is an AI platform transforming mortgage servicing by automating loan processing, payment collections, and dispute resolution. We work with some of America’s largest mortgage lenders, helping them scale 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

We’re looking for a Founding Backend Engineer to build and optimize Kastle’s AI infrastructure. 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, distributed systems, and AI integration—ideal for an engineer who thrives in high-impact environments.

Responsibilities

• Architect and develop scalable backend services for AI-driven mortgage servicing 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.
• Ensure security and compliance with financial regulations (SOC 2, FDCPA, RESPA, TILA).
• 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.
• Experience with containerization and orchestration tools, including Docker and Kubernetes.
• Proficiency in designing and optimizing distributed systems, with a focus on high-availability architectures.
• 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.
• Knowledge of API security best practices (OAuth, JWT, rate-limiting).
• Experience with CI/CD pipelines and DevOps tools.
• Excellent problem-solving skills and a passion for optimizing backend performance.

Preferred Qualifications

• Background in AI/ML-powered systems, especially LLM applications.
• Experience working with financial services or compliance-heavy industries (fintech, lending, insurance).
• Previous startup experience, with a hands-on approach to problem-solving.

Why Join Kastle?

• Build and scale AI applications that are transforming mortgage servicing.
• 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 a chance to be a foundational team member.