Staff Backend Engineer - Payments Platform (Greenfield)

The Onset; Sydney; On-site; AUD 180,000 - 280,000; Full time

Job summary

The Onset is building a greenfield payments and billing platform in Sydney. You’ll join a small founding team as a Staff/Principal Backend Engineer, shaping core architecture and API design.

You’ll own how services interact, ensure reliability, and drive decisions in a fast-moving, autonomous environment. Lead backend work across payments, pricing, and APIs, with a strong emphasis on correctness and scalability in a cloud-native setting.

Qualifications

• Strong Java/JVM experience with distributed backend systems.
• Experience designing and building payment/billing infrastructures.
• Ability to own complex technical decisions end-to-end.

Responsibilities

• Design and own backend components for payments & billing platform.
• Define service boundaries and API designs for customers building on the platform.
• Ensure reliability, performance, and observability of core infrastructure.
• Collaborate with founders to shape architecture and engineering standards.

Skills

Java

JVM

Distributed systems

APIs

Cloud infrastructure

Backend architecture

Ownership

Tools

Spring

Kubernetes

Job description

The Onset is building a greenfield payments and billing platform in Sydney. You’ll join a small founding team as a Staff/Principal Backend Engineer, shaping core architecture and API design.

You’ll own how services interact, ensure reliability, and drive decisions in a fast-moving, autonomous environment. Lead backend work across payments, pricing, and APIs, with a strong emphasis on correctness and scalability in a cloud-native setting.