Principal Software Engineer

Principal Engineer
About the role
We are building an AI platform that helps workers, business owners and specialist advisers work out what Australian employment law requires and what the correct pay is. Award rules shift with age, classification, seniority and hours, and they change every year. Recent reforms have raised the stakes considerably, with underpayment now attracting criminal penalties in serious cases. Our platform determines which award and classification apply, calculates entitlements from published rates and rules, and records how every answer was reached, so the result can be relied on and defended.
As our Principal Engineer, you will be the senior engineering voice in Sydney and work directly with the founders. Our development team is based overseas, and this role sets the engineering standard they build to and owns the technical quality of everything that reaches production. The core of the product is a deterministic calculation engine, a versioned library of legal instruments and pay rates, and a verification layer that declines to answer when an answer cannot be grounded in source. You will be accountable for building those to a standard that holds up under audit. The role is based in Sydney.
Key responsibilities
• Lead the technical build of the platform's core components: the calculation engine, the instrument and rates data model, document ingestion, and the retrieval and verification layer. The calculation engine is the foundation of the product and the core of the role.
• Turn approved solution designs into working architecture and code, working closely with the Principal Solution Designer and resolving gaps between design and build early.
• Set and enforce engineering standards across the team, including code review, automated testing, continuous integration, documentation and architecture decision records.
• Provide day-to-day technical leadership to our overseas development team, including design review, pairing and final review of work before it is merged.
• Own the platform's performance and stability: load testing, response times, monitoring and alerting, so the system behaves predictably as usage grows.
• Build security and privacy in from the start, including Australian data residency, access control, secrets management and safe handling of the payslips and payroll data users upload.
• Integrate large language models as replaceable components, with evaluation and guardrails, and keep them out of any part of the system that produces a number.
• Lead the engineering work for each annual award rate change, so updated rules are tested and released before they take effect.
Selection criteria
Essential
• Substantial software engineering experience, typically ten or more years, including technical leadership of systems running in production.
• Strong backend engineering in a modern language such as Python, TypeScript or Java, with deep experience in relational databases and data modelling.
• Experience building rules-driven or calculation-heavy systems where results must be correct, reproducible and explainable, such as payroll, billing, tax, insurance or financial systems.
• Hands-on experience with cloud infrastructure (AWS preferred), CI/CD pipelines, automated testing and observability.
• Experience leading or reviewing the work of distributed or offshore development teams, with the judgement to raise quality without slowing delivery.
• Clear written communication. You will explain technical trade-offs to the founders and document decisions so others can build on them.
Desirable
• Experience building applications on large language models, including retrieval, evaluation and guardrails.
• Experience with versioned or time-based data, where the system must answer what was true at a past date.
• Exposure to payroll, workforce management, legal technology or financial services.
• Familiarity with the Australian Privacy Principles and data residency requirements.
What we offer
• Direct involvement at an early stage of the company, with regular access to the founders and real influence over technical direction.
• Ownership of the engineering foundations the entire product depends on.
• A demanding engineering problem: a system whose every output must be correct, traceable and defensible.
How to apply
Please submit your CV together with a brief statement outlining your interest in the role and the problem we are solving. We value concise, considered applications over length.