Principal Software Engineer

About the role

Calibrex is hiring a Principal Software Engineer to be a decisive, hands-on technical leader as we build and scale our products. You will own the architectural judgment behind the systems we build: making thoughtful trade-offs, identifying the decisions that need to be durable, and helping us move quickly without creating expensive problems for our future selves. You will work closely with the founding team to turn ambitious product ideas into reliable, maintainable software. This is not an architect-from-the-sidelines role. You will design critical systems, write and review production code, improve how we ship and operate software, and raise the engineering bar through clear technical direction and mentorship.

We use AI-assisted development tools—including Codex and Claude—to accelerate our work. We are looking for someone who can get the most from those tools while bringing the judgment to validate output, establish sound patterns, and make the architectural calls that tools alone cannot make. This is a senior individual-contributor role with meaningful autonomy and influence across the product. It does not require direct people management but will require working with the CTO to develop product development roadmaps, deliverables, and timing.

Requirements

• 8+ years of professional software engineering experience, including ownership of production systems at meaningful scale
• A demonstrated track record of architecting, building, and operating a complex application or platform through growth
• Excellent systems-design judgment across application architecture, APIs, data, infrastructure, reliability, security, and performance
• Ability to make pragmatic technical trade-offs with incomplete information, balancing speed, simplicity, and long-term maintainability
• A deeply hands-on approach to building, debugging, reviewing, and improving production software
• Experience setting engineering standards and guiding other engineers through design reviews, code reviews, and technical decisions
• Strong written and verbal communication, including the ability to explain technical choices clearly to founders and non-technical partners
• Comfort working in a high-autonomy environment where priorities and product requirements evolve quickly

Preferred experience

• Built or substantially evolved a product used at significant scale
• Led a major architectural migration or modernization
• Worked in an early-stage or high-growth company
• Designed systems for high availability or sensitive user data
• Established effective AI-assisted engineering workflows with strong verification practices
• Experience across client applications, cloud infrastructure, backend services, and data management at scale

Skills

• System architecture
• Distributed systems and API design
• Cloud infrastructure
• Reliability and observability
• Security and privacy engineering
• Technical leadership
• AI-assisted software development

Benefits

• Annual performance-based cash bonus
• Generous equity package
• Great benefits

This role is an excellent wealth-building opportunity at a fast-growing pre-IPO company in a nascent and extremely exciting space.