Staff Engineer, Growth

Affix; City of Melbourne; Hybrid; AUD 140,000 - 200,000; Full time

Job summary

PayRewards, the US growth arm of pay.com.au, seeks a senior growth engineer to own end-to-end delivery of high-impact features for the US market. You’ll shape the experiment design, ship AI-driven solutions, and drive analytics across the growth surface, reporting to the CTO and collaborating with the CEO and Product Manager.

You’ll work on a PCI DSS–compliant payments platform with responsibility for architecture and performance, applying a strong growth mindset and self-direction to build

Qualifications

• Engineers with Staff, TL, Principal or EM experience who have owned architecture, reviewed others' work and been accountable when it broke.

Responsibilities

• Own architecture and execution of growth-driven features from end to end.
• Design and ship experiments with measurable impact and iterate based on results.
• Support a high-standard payments/engineering platform architecture and collaborate across the team.

Skills

Full stack

AI development tooling

Analytics

Experiment design

Job description

• Funding: Raised approximately US$70 million in total funding since 2019, including its US$28 million Series E in August 2026 for US expansion.
• Location: Windsor, Melbourne
• Ways of working: Hybrid, office 3 days a week (Mon, Tues & Thurs)

The Story

PayRewards is pay.com.au's US business: American small businesses pay their suppliers by card and earn rewards on money they were already spending, including points that move straight into airline programs. The model is already proven at home. Since launching in 2021, pay.com.au has taken 100,000+ Australian businesses onto the platform, processed billions in payments, picking up a #1 Smart50 and a #3 AFR Fast Starters finish in the process. The US side sits in front of a small business market roughly twelve times the size of Australia's, and the plan is to make it several times its current size within the year.

The Role

This is the first growth engineering hire on the US business, and you'll join the US Squad as its most senior engineer. There's no roadmap and no card waiting to be written when you start: you find the opportunity, build it, measure it, and decide what happens to it. Registration, activation, referral and affiliate, in-product conversion, landing experiences: it's yours to ship, behind a toggle, instrumented and reversible, with no approval step in the way. When an experiment doesn't work, you're expected to end it with a number rather than let it linger.

Underneath the growth surface is a licensed, PCI DSS compliant and ISO 27001 certified payments platform, and you'll hold a high standard on that core platform too: architecture, review, and lifting the engineers around you. You'll report to Dee Kulkarni, CTO, and work day to day with Blake Hutchison, CEO of PayRewards US, and the Product Manager. An experiment you ship on Tuesday shows up in the numbers on Friday, with no layers in between.

Real fluency with AI development tooling is part of that, with opinions about it you've earned rather than read. This isn't AI as an assist for tests or documentation: agentic loop development is how you ship, agents form the core of how software gets to production here, and Pay's engineering practices are baked into how they work.

Why This Is Interesting

You get product judgment, growth accountability and AI-native delivery in one seat, as the most senior engineer on a squad in a business that's already proven the model once. It's a genuine build-from-zero mandate: what the growth surface covers and how an experiment gets decided is yours to define rather than inherit. Five years took the Australian business from nothing to 100,000+ customers and a top-three AFR Fast Starters finish, with engineering growing from under 10 people to 47 along the way. The US build is at the start of its own version of that curve, backing a Melbourne engineer to run it from HQ, on Melbourne hours.

Who Should Apply

Engineers with Staff, TL, Principal or EM experience who've owned architecture, reviewed other people's work, and been accountable when it broke. You're full stack and comfortable shipping a customer-facing feature front to back on your own, genuinely fluent with AI development tooling and comfortable enough with analytics and experiment design to read your own results honestly, including when they disagree with you. A background in B2B SaaS or another service business is what matters most; payments experience is welcome but not required. You'll do best here if you're self-directed, since nobody will be assigning you work on the regular.