Senior Software Engineer, Java (Hybrid — Denver Metro preferred)

FusionAuth•Denver, CO

46d•$140,000 - $180,000•Hybrid

About The Position

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.

Requirements

8-10 years of professional software development experience, with demonstrated ownership of complex features from design through release.
Bachelor's degree in computer science, or demonstrable experience with a broad set of theoretical topics.
Advanced Java skills, including threading, concurrency, and performance profiling.
Strong object-oriented design and implementation skills.
Solid understanding of the full web stack (HTTP, TCP/IP, REST, and related protocols).
Real working knowledge of relational databases: query optimization, indexing strategy, and schema design beyond ORM abstractions.
Experience designing test approaches for complex features and writing end-to-end tests, not just unit tests.
Comfortable working up and down the stack, including cloud infrastructure, backend services, and JavaScript on the front end.
Comfortable using Claude Code, or a comparable AI-assisted development tool, as part of your daily workflow.
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.

Nice To Haves

Experience building highly available, high-performance, multi-threaded, API-first applications.
Working knowledge of OAuth 2.x grant types, OIDC protocol depth, and authentication enterprise integration patterns.
Experience writing a basic manifest or Helm chart, with some familiarity with container orchestration in production.
Experience writing GitHub Actions workflows or comparable CI/CD pipelines.
Strong, data-driven approach to solving problems.
Quick learner, comfortable mastering new technologies and skills rapidly.
Holds clear technical opinions while staying open to better evidence or team input.
Appreciates first-principles thinking, but knows when to stop theorizing and start building.
Adaptable to the pace and ambiguity common in a roughly 50-person startup.

Responsibilities

Design and build complex features end-to-end, from technical design through release.
Write high-quality, secure, well-tested production code.
Author Technical Design Documents (TDDs) and provide architecture recommendations on designs led by others.
Serve as reviewer of record for parts of the codebase. Review for correctness, test quality, and architectural fit.
Design test approaches for complex features, write end-to-end tests for critical paths, and evaluate test quality during code review.
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).
Optimize queries using indexes and constraints.
Understand ORM tradeoffs and have basic NoSQL familiarity.
Apply least-privilege principles and understand timing attacks and encryption basics (PKI vs. symmetric).
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.
Identify areas of tech debt and propose focus areas for the team.
Present designs and tradeoffs to Product, DevSuccess, and Support. Translate technical constraints for non-engineering partners.
Influence team decisions through clear reasoning. Support and sometimes lead knowledge-sharing sessions on FusionAuth's architecture.
Join customer calls to discuss specific technical topics and support complex integration questions.
Write clear, thorough documentation for the features you ship.

Benefits

Comprehensive health insurance including medical, dental, and vision coverage, with the company covering the majority of your medical premiums to keep your costs low
Fully employer-paid High Deductible Health Plan (HDHP) option paired with a Health Savings Account (HSA), including employer contributions
Basic life insurance and short- and long-term disability coverage fully paid by the company for essential financial protection
Voluntary life insurance options to provide additional financial protection for you and your loved ones
Healthcare and Dependent Care Flexible Spending Accounts (FSAs) to save pre-tax dollars on eligible expenses
401(k) plan with company match to help you save for retirement
Generous paid time off (PTO) plus paid company holidays to support work-life balance
Employee Assistance Program (EAP) offering confidential counseling and support services
Professional growth and development opportunities to boost your career journey
Eligibility for performance-based bonuses or variable compensation tied to individual, team, or company results