Senior Software Engineer, Java (Hybrid, Denver Metro Preferred)

Job Title: Senior Software Engineer, Java
Location: Denver, CO preferred (Hybrid)

About FusionAuth

FusionAuth is a fast-growing startup and leading provider of customer identity and access management (CIAM) software headquartered in Denver, Colorado. Our mission is to make authentication and authorization simple and secure for every developer. Our product helps businesses securely manage customer identities and access, ensuring a safe user experience for some of the largest brands in the world. We are committed to delivering exceptional value and satisfaction to our clients through top-notch service and support. With a great team and strong investors, we are expanding our team to help accelerate our growth and take FusionAuth to the next level.

Job Summary

FusionAuth is hiring a Senior Software Engineer to build and extend our Java-based platform, trusted by thousands of organizations and downloaded over 10 million times. You will design and ship complex features end to end, from technical design through release, and apply protocol knowledge (OAuth 2.x, OpenID Connect, SAML) that customers rely on for correct, secure implementations.

This is a senior individual contributor role with real influence. You will review code for correctness and architectural fit, mentor Software Engineers on debugging and testing approaches, and identify tech debt before it slows the team down. You will partner directly with Product, DevSuccess, and Support to translate technical tradeoffs into decisions the business can act on.

Every feature you ship runs across customer-managed, self-hosted, and dedicated cloud deployments, so backward compatibility and upgrade paths matter on every change. This position reports to the Engineering Manager.

Responsibilites:

• Feature development: Design and build complex features end-to-end, from technical design through release. Write high-quality, secure, well-tested production code.
• Technical design: Author Technical Design Documents (TDDs) and provide architecture recommendations on designs led by others.
• Code and design review: Serve as reviewer of record for parts of the codebase. Review for correctness, test quality, and architectural fit.
• Testing: Design test approaches for complex features, write end-to-end tests for critical paths, and evaluate test quality during code review.
• Debugging and troubleshooting: Diagnose and fix multithreaded and concurrency issues. Handle complex issues, including on-call rotation for critical customer issues (off-hours support required, though not the norm).
• Database: Optimize queries using indexes and constraints. Understand ORM tradeoffs and have basic NoSQL familiarity.
• Security: Apply least-privilege principles and understand timing attacks and encryption basics (PKI vs. symmetric).
• AI-augmented development: Use LLMs as part of the SDLC, including code review assistance, documentation drafting, and refactoring. Help the team rethink how work gets done with AI in the loop.
• Technical roadmap: Identify areas of tech debt and propose focus areas for the team.
• Cross-functional communication: Present designs and tradeoffs to Product, DevSuccess, and Support. Translate technical constraints for non-engineering partners.
• Technical influence: Influence team decisions through clear reasoning. Support and sometimes lead knowledge-sharing sessions on FusionAuth's architecture.
• Customer engagement: Join customer calls to discuss specific technical topics and support complex integration questions.
• Documentation: Write clear, thorough documentation for the features you ship.

Qualifications

If you meet most of the required qualifications below but not all of them, apply anyway. Skills transfer, and we'd rather talk to you than miss you over a checklist.

Required

• Experience: 8-10 years of professional software development experience, with demonstrated ownership of complex features from design through release.
• Education: Bachelor's degree in computer science, or demonstrable experience with a broad set of theoretical topics.
• Java: Advanced Java skills, including threading, concurrency, and performance profiling.
• Object-oriented design: Strong object-oriented design and implementation skills.
• Web fundamentals: Solid understanding of the full web stack (HTTP, TCP/IP, REST, and related protocols).
• Database depth: Real working knowledge of relational databases: query optimization, indexing strategy, and schema design beyond ORM abstractions.
• Testing: Experience designing test approaches for complex features and writing end-to-end tests, not just unit tests.
• Full-stack range: Comfortable working up and down the stack, including cloud infrastructure, backend services, and JavaScript on the front end.
• AI tooling: Comfortable using Claude Code, or a comparable AI-assisted development tool, as part of your daily workflow.
• Work location: FusionAuth is headquartered in the Denver metro area, and we value the collaboration that comes from working together in person. We strongly prefer candidates local to the Denver metro who can be onsite 1-2 days per week. We're open to candidates in other locations who are willing to travel to our office approximately once per quarter.

Preferred:

• Distributed systems: Experience building highly available, high-performance, multi-threaded, API-first applications.
• Auth protocols: Working knowledge of OAuth 2.x grant types, OIDC protocol depth, and authentication enterprise integration patterns.
• Kubernetes: Experience writing a basic manifest or Helm chart, with some familiarity with container orchestration in production.
• CI/CD: Experience writing GitHub Actions workflows or comparable CI/CD pipelines.
• Quantitative approach: Strong, data-driven approach to solving problems.
• Learning speed: Quick learner, comfortable mastering new technologies and skills rapidly.
• Communication style: Holds clear technical opinions while staying open to better evidence or team input.
• Pragmatism: