Senior Fullstack Engineer (Frontend Leaning)

The Onset; Sydney; On-site; AUD 140,000 - 200,000; Full time

Job summary

The Onset Group in Sydney is seeking a Senior Fullstack Engineer (Frontend Leaning) to join a greenfield data platform project. You will design a data-rich web app and help activate customer audiences across digital channels.

Work on frontend-heavy features using React and TypeScript, build dashboards, and collaborate with backend services. This 6-month contract may extend, with opportunities to influence architecture and engineering standards across the stack.

Qualifications

• Strong commercial experience building complex applications with React and TypeScript.
• Solid full stack engineering experience, including backend development and API integration.
• Experience building greenfield products or owning major features from design through to delivery.
• Strong understanding of frontend architecture, component design, state management and application performance.
• Experience working with data-heavy applications, dashboards, workflow tools or complex business logic.
• Ability to make sound technical decisions and work through ambiguous requirements.
• Strong communication skills and the ability to work closely with technical and non-technical stakeholders.
• A hands-on engineering approach, regardless of seniority.

Responsibilities

• Designing and building a complex, data-rich web application using React and TypeScript.
• Developing interactive dashboards, audience management tools and advanced filtering interfaces.
• Building rule-based segmentation tools with nested conditions, dynamic filters and complex user interactions.
• Integrating frontend applications with backend services, APIs and data platforms.
• Contributing to technical architecture, application design and engineering decisions.
• Working with engineers and business stakeholders to turn complex requirements into practical solutions.
• Helping establish engineering standards, reusable components and maintainable application architecture.
• Taking ownership of features from initial design through to production.

Job description

Senior Fullstack Engineer (Frontend Leaning)

Senior / Staff Full Stack Engineer (Frontend Leaning) Location: Sydney, NSW

Engagement: 6-month contract + extension

The Opportunity

We're working with a large Australian organisation looking for an experienced Full Stack Engineer with strong

frontend expertise to help build a new customer data and audience activation platform.

This is a greenfield engineering opportunity where you'll help shape a complex, data-driven application from the

The platform will bring together customer data, audience segmentation and advertising activation into a single

application, giving teams better tools to create, manage and activate customer audiences across digital

channels.

What You'll Be Working On

• Designing and building a complex, data-rich web application using React and TypeScript.
• Developing interactive dashboards, audience management tools and advanced filtering interfaces.
• Building rule-based segmentation tools with nested conditions, dynamic filters and complex user interactions.
• Integrating frontend applications with backend services, APIs and data platforms.
• Contributing to technical architecture, application design and engineering decisions.
• Working with engineers and business stakeholders to turn complex requirements into practical solutions.
• Helping establish engineering standards, reusable components and maintainable application architecture.
• Taking ownership of features from initial design through to production.

What We’re Looking For

• Strong commercial experience building complex applications with React and TypeScript.
• Solid full stack engineering experience, including backend development and API integration.
• Experience building greenfield products or owning major features from design through to delivery.
• Strong understanding of frontend architecture, component design, state management and application performance.
• Experience working with data-heavy applications, dashboards, workflow tools or complex business logic.
• Ability to make sound technical decisions and work through ambiguous requirements.
• Strong communication skills and the ability to work closely with technical and non-technical stakeholders.
• A hands-on engineering approach, regardless of seniority.

Nice to Have

• Experience with Java, Kotlin or JVM-based backend services.
• Exposure to cloud platforms, distributed systems or event-driven architectures.
• Experience building SaaS platforms, internal products, analytics tools or data management applications.
• Experience working with customer data, advertising technology, retail technology or audience segmentation.
• Experience mentoring engineers or contributing to broader technical direction.

Why Consider This Opportunity?

You’ll have the opportunity to help shape a new product from its early stages, influence technical decisions and

build software used to manage complex customer data and advertising workflows.

The work combines modern frontend engineering with meaningful backend integration, complex business logic

It’s particularly suited to engineers who enjoy building products from scratch, taking ownership and working

across the stack without losing their frontend specialisation.

Interested?