Senior Software Engineer (Node.js/React)

Location: San Mateo, CA

Department: Loan Origination

About the role

The Mortgage Office is looking for a Senior Software Engineer (Back-End) to architect and scale the core systems powering our platform.

This is a backend-leaning full stack role (~70% backend, 30% frontend). We need a true backend builder who can design and implement scalable, secure microservices, while also being comfortable contributing to our React-based frontend when needed.

This is not a support role. This is a high-ownership engineering role focused on system design, API development, data architecture, and secure multi-tenant SaaS systems.

What you'll do

• Architect and implement scalable backend services using Node.js (Nest.js framework) in a microservices environment
• Design and build APIs from scratch — including schema design, validation, authentication, and lifecycle management
• Own database design, optimization, and data modeling
• Build and maintain data pipelines, messaging systems, and analytics storage
• Contribute to frontend development in React to support end-to-end feature delivery
• Collaborate cross-functionally to deliver complete features from backend services to UI
• Drive architectural decisions that improve scalability, performance, and security
• Backend Focus & Requirements (Core of the Role)

Microservices Architecture

• Hands-on experience building services using Nest.js
• Strong understanding of distributed systems and service communication patterns

API Ownership

• Built APIs (not just consumed them) within the last 2–3 years
• Experience designing RESTful or event-driven APIs
• Familiar with versioning, validation, documentation, and testing strategies

Data & Systems Depth

• Strong database design experience (schema design, indexing, performance tuning)
• Experience building data pipelines and working with messaging systems
• Experience with analytics storage and reporting systems

End-to-End Security Understanding

• Deep understanding of authentication flows and token management (JWT, OAuth, etc.)
• Experience designing or operating within multi-tenant architecture
• Strong awareness of common security vulnerabilities and prevention methods
• Experience implementing role-based access controls and secure API patterns

Frontend Expectations (30%)

• Strong working experience with React
• Ability to build and maintain production-ready UI components
• Comfortable connecting frontend to backend APIs you’ve built
• Understanding of state management and frontend performance optimization

Qualifications

• 5+ years of full stack experience, with strong backend depth
• Experience owning systems or features from design through deployment
• Strong systems-thinking mindset
• Ability to operate independently in a high-impact role
• Experience in SaaS or multi-tenant environments is highly preferred

Why Join Us?

• Comprehensive health, dental, and vision coverage.
• 401(k) with company funded match.
• Mission-driven company with a 45+ year legacy and industry-leading products trusted by thousands of lenders.
• Collaborative, supportive team known for long tenure, deep expertise, and a culture built on trust and integrity.
• Help modernize and evolve the leading platform in private lending technology.
• Beautiful San Mateo office with a tight-knit culture.
• Competitive compensation and room for professional growth.
• Performance-based bonuses.
• Generous PTO. 
• Modern workspace with on-site amenities.
• Awesome company Christmas party.

About the Company

About Applied Business Software, Inc.,

Applied Business Software, Inc., (ABS), the maker of The Mortgage Office®, is the industry leader in private lending and loan management technology. Since 1978, our software has powered thousands of lenders, including private money firms, municipalities, CDFIs, Tribal Nations, universities, franchisors, third-party servicers and other non-bank lenders, helping them streamline, automate, and scale their lending operations with confidence.