Principal Engineer

Checkbox is a Series A, Sequoia-backed technology start-up with a mission to enable meaningful work for all. We are building an AI-first platform that is transforming how in-house legal teams operate, from how work enters legal through to how it is understood, routed, managed and resolved.

Our customers include leading in-house legal teams at companies such as SAP, Coca-Cola, Allianz, BMW, Elastic and Stryker.

We are now expanding beyond workflow automation into AI-powered intake, matter management, triage and work orchestration. Our vision is to become the Legal Service Hub for modern organisations, responsible for how legal work is raised, allocated, managed and resolved.

As we scale our product, engineering organisation and AI capabilities, we need our architecture to stay coherent, secure and built for the future. This role sits at the centre of that.

The Role

We are looking for a hands-on Principal Engineer to act as the senior technical authority across Checkbox’s product engineering streams.

This role is accountable for making, recording and governing the key technical decisions that shape our future-state product architecture. That includes high-consequence, hard-to-reverse “one-way-door” decisions that are expensive to undo and should not be made implicitly inside a single team.

You will help keep our architecture sound, coherent across product streams and safe as we scale. Just as importantly, you will ensure important decisions are written down, understood and followed, rather than lost in tribal memory.

This is a technical leadership role, not a people-management role. You will influence through judgement, clarity and working code.

What You’ll Own

• Own key architecture decisions across Checkbox’s product engineering streams, including high-consequence one-way-door decisions

• Define, document and govern the future-state product architecture

• Ensure architecture remains coherent across product streams, Platform, Data Engineering, QA, Enterprise IT and other technology teams

• Identify, design and help build force-multiplier initiatives that help engineering teams move faster and ship higher-quality software

• Contribute directly to production releases and set the technical bar through working code

• Drive engineering decisions through data, feedback loops and measurable quality signals rather than opinion alone

• Embed fitness functions, architecture measures and technical feedback loops into how product engineering works

• Partner closely with the Data Engineering function on the data and AI reference architecture

• Ensure tenancy, security and compliance are designed into systems from the start

• Work closely with Product, Customer Success and Sales so architecture decisions reflect real customer and commercial needs

• Support teams in making pragmatic technical trade-offs between speed, scale, quality, security and maintainability

About You

• Significant experience as a Principal Engineer, Staff Engineer, Architect or senior technical leader in a modern SaaS environment

• Deep systems expertise across product engineering, platform architecture, distributed systems and modern cloud-native software

• Strong track record of making and governing high-impact architecture decisions across multiple teams or product areas

• Proven ability to design and ship force-multiplier technical initiatives that improve engineering velocity, quality or reliability

• Comfortable contributing to production systems while also setting broader technical direction

• Strong understanding of tenancy, security, compliance and data isolation in enterprise SaaS environments

• Experience working closely with platform, data, QA, infrastructure or enterprise IT teams

• Strong product and customer judgement, with the ability to connect technical decisions to commercial and customer outcomes

• Ability to influence through credibility, clarity and working code rather than formal authority

• Excellent communication skills, with the ability to bring technical and non-technical stakeholders along

• Pragmatic, hands-on and comfortable operating in a fast-moving scale-up environment

Bonus Points

• Experience working on AI-native products, agentic systems, workflow automation or enterprise legal technology

• Experience defining architecture across multiple product streams or a multi-product SaaS ecosystem

• Experience designing systems that rely on context, retrieval, eventing, integrations or AI-enabled workflows

• Experience partnering with data engineering teams on AI or data reference architecture

• Experience introducing engineering fitness functions, architectural decision records, technical standards or quality measures

• Experience working in a Series A, Series B or high-growth scale-up environment

What We Offer

• Competitive salary

• Hybrid working with team days in our Sydney CBD office

• High ownership over architecture decisions that shape Checkbox’s product and engineering future

• Direct impact across product engineering, platform, data and AI systems

• Opportunity to help scale an AI-first SaaS platform used by leading enterprise legal teams

• Personal learning and development budget

• Flexible leave policy

• Expense policy and salary sacrifice options

• CBD start-up hub with snacks, drinks, premium coffee and team socials

• Company-wide social events and annual off-sites

• Transparent, flat culture where questions and feedback are welcomed