Principal Software Engineer

About Willow

Buildings are more complex than ever — and the teams responsible for running them are still working with fragmented tools, disconnected data, and reactive workflows. Willow is changing that. We build the leading Operational AI platform for the built world, helping owners and operators of large, complex environments — think commercial real estate, higher education, healthcare, and airports — better understand, manage, and optimize their buildings by connecting physical, operational, and human data into a unified digital foundation.

Our platform enables customers to move from reactive workflows to smarter operations, better decision-making, and meaningful financial and operational outcomes. We're a small but mighty company with real customers, real traction, and a genuinely important problem to solve — scaling commercial momentum and building the foundation for long-term category leadership. If you want to do meaningful work at a company that's defining a category, this is the place.

About the role

You’ll help set the technical direction for Willow’s platform and be hands-on in the code every day, personally taking on some of our biggest technical challenges. You’ll shape architecture across teams, set engineering standards, and mentor engineers so that we ship secure, reliable, high-quality software at scale. This is a senior individual contributor role, not a people-management position.

You’ll work across Engineering, Product, Customer Engineering, Sales and Marketing, and with partners, often across time zones. We’re looking for someone who has had real influence across a whole company, not just a single team.

What you'll own

Architecture & technical direction

• Own the architecture of complex, cloud-based systems on Azure, including containers, graph storage, LLMs, and a wide range of Azure services.
• Stay hands-on: write production code and lead the design of new initiatives.
• Design integrations with partners and customer systems that work smoothly across multiple companies.

Engineering standards & quality

• Set technical standards, such as approved languages, libraries, Azure resources and framework versions, and make sure teams apply them consistently.
• Raise the bar on code quality, observability and reliability across all of Willow’s software, including design and code reviews across teams.
• Lead secure engineering practices and keep reducing vulnerabilities.

Cross-functional partnership

• Work with Product to shape the product vision and explain trade-off decisions in terms of customer value.
• Partner with Customer Engineering, Sales and Marketing to turn business needs into technical solutions.
• Advise senior leadership on technical and product strategy.

Mentorship & engineering culture

• Mentor senior and lead engineers.
• Build a culture of transparency, knowledge sharing and continuous improvement.
• Help teams use AI tools well in how they build, and in what we build.

What success looks like in year one

• Determine a path forward for Willow’s building topology graph storage that is secure, performant, cost-effective, and scalable, working closely with key Willow partners on cutting-edge solutions to difficult problems.
• Own the features that make data in the graph available to the Willow Copilot AI platform and other parts of the platform.
• Work daily with other developers at Willow to optimize the entire application platform, resolve issues, and design the architecture Willow needs to scale rapidly as we grow.

What we're looking for

Required

• 10+ years of commercial software development, including senior or principal-level technical leadership
• Deep expertise in C# and modern .NET, plus working knowledge of TypeScript, React and Python
• A track record of designing, building and running distributed systems on Azure, using its PaaS services in production
• Strong command of design patterns and software architecture, and the ability to teach them to others
• Hands-on experience with CI/CD, infrastructure as code and DevOps practices
• Proven influence across teams and functions, with company-level technical decisions you can point to
• A security-first mindset, with experience leading secure development practices
• Clear writing and strong asynchronous communication with distributed teams across time zones
• Hands-on use of AI tools in your day-to-day work, and the ability to speak knowledgeably about how you use them

Preferred

• IoT, digital twin or building-systems data (for example time series and graph data, or Azure Digital Twins / Microsoft Fabric)
• AI/ML in production: LLM platforms, MLOps pipelines, or AI features built into a SaaS product

Nice to have

• Data platforms such as Snowflake or Azure data services
• Pulumi or similar infrastructure-as-code tooling, plus Grafana or other observability tools
• Experience at a global start-up or scale-up

How you work

• You design systems to optimize growth, performance, and cost.
• You take pride in ownership and in your ability to deliver results and ship stable features.
• You thrive when working with others, building consensus, and growing the entire team.

Who we can picture in this role

Two people we can picture in this role. The first is a senior developer from a large organization who is strong on the Azure stack, and is ready to take on ownership of major projects, work with new technologies, and become a leader. The second is someone who has spent time in the startup space as a principal engineer, has experience scaling an entire company from a few customers to hundreds, and can see around the corners on the path to 10x growth. These are illustrations, not a specification — if you are neither of these but have the skills and experience the role needs, we would still very much like to hear from you.

Compensation & Benefits

$200,000 – $220,000base salary per year

Exact offer reflects your experience and skills.

In accordance with applicable state pay transparency laws, the salary range and a general description of all benefits and other compensation have been disclosed herein. Actual compensation will be determined based on experience, skills, and other relevant factors.