Founding Staff Engineer - Frontend

Own the frontend architecture of an early-stage software platform, from the JavaScript SDK other engineers integrate to the checkout experiences their customers use.

We’re partnering with a Sydney startup building infrastructure that helps software companies manage pricing, subscriptions, billing and payments. The founders have built monetisation systems at scale and are now bringing that experience to a new product.

As a founding frontend engineer, you’ll work directly with the founders and early customers. The architecture is still taking shape, giving you scope to make the decisions that future engineers will build on.

What you’ll build

• Embeddable checkout and upgrade experiences that work inside customers’ products and feel native to their brands.
• A JavaScript/TypeScript SDK that makes integration straightforward for external developers.
• A reusable component library and design system across embedded experiences and the customer portal.
• Interfaces that help customers manage pricing, run experiments and understand revenue performance.
• The frontend standards for performance, accessibility, testing and safe releases.

The technical challenge is substantial: your code needs to work reliably inside applications you don’t control. You’ll solve problems around browser behaviour, CSS and script isolation, bundle size, security and compatibility, while keeping the experience simple for users.

What you’ll bring

You’ll have personally owned significant frontend architecture decisions and still enjoy writing production code.

We’re looking for:

• Deep JavaScript/TypeScript knowledge and strong browser fundamentals.
• Experience building complex frontend systems with React.
• Ownership of SDKs, reusable component platforms, design systems or similar frontend foundations.
• Good product judgement, including the ability to turn complex workflows into clear interfaces.
• Confidence making technical decisions in an early-stage environment, working closely with founders and customers.

Experience with public JavaScript SDKs, embedded widgets, Web Components, Shadow DOM or iframes would be particularly relevant. Payments experience is useful, but isn’t essential.

Why join?

You’ll join while the key technical decisions are still open. You’ll have direct input into the product, learn from real customer integrations and see how your work affects the way people buy and use software.

This is a hands-on Staff/Principal opportunity with ownership across architecture and delivery. It suits someone who wants to build the foundations, stay close to the code and help shape a growing engineering team.

The frontend uses TypeScript and React, supported by a Java backend on AWS with PostgreSQL. Your focus will be frontend engineering, with close collaboration on API design.

Apply now or contact Matt at The Onset for a confidential conversation.