Senior Backend Engineer – Distributed Systems (C#/.NET)

Are you a senior backend engineer who thrives on distributed systems, clean architecture, and complex data problems? At ONYX Insight, we're looking for a Senior Software Developer (Contractor) to make an immediate impact on our core platform, a sophisticated distributed system processing data from wind turbines around the world. This is not a typical SaaS CRUD role. You'll work across a distributed architecture including asynchronous messaging, worker processes, and data ingestion pipelines. Frontend exposure is a bonus, not a requirement.

Key Responsibilities:

• Backend Delivery: Implement robust, well-tested C# .NET services following clean architecture principles — domain logic, data access, messaging, and background processing.
• Distributed Systems: Contribute to service boundary design, asynchronous messaging flows, and worker processes within our modular monolith, with an eye on future decomposition.
• Data Pipelines: Build and maintain backend ingestion flows that sanitise, standardise, and process high-volume sensor data reliably and at scale.
• Code Quality: Write clean, well-tested code with strong unit and integration coverage. You care about correctness, not just delivery.
• Collaboration & Deployment: Support frontend engineers with clean API contracts, and contribute to our CI/CD pipeline and artifact-based deployment process.

Ideally, you'll have/be:

• Deep, commercial C# .NET experience (5+ years) — comfortable with clean architecture, SOLID principles, and building maintainable systems at scale.
• Solid experience with distributed systems and async patterns — service buses, message queues, background workers, and event-driven architecture. You understand the tradeoffs, not just the tooling.
• Experience building data ingestion or processing pipelines — handling high-volume, real-world data with a focus on reliability and fault tolerance.
• Strong PostgreSQL skills — schema design, migrations, and efficient queries against complex data models.
• A genuine testing culture — unit and integration tests written as standard, with an understanding of what makes a test suite valuable.
• Familiarity with AWS and how backend services are deployed and monitored in production.
• Experience with modular or service-oriented architectures — you appreciate well-defined boundaries and can work pragmatically within a monorepo.
• A contractor mindset: self-directed, fast to ramp up, and able to deliver independently — while communicating clearly when things need to be challenged.
• Some React or TypeScript exposure is useful, but frontend delivery is not an expectation of this role.

About ONYX

ONYX Insight is a growing technology and engineering organisation in the renewable energy sector. Our vision is to build a more efficient future by becoming the world's most innovative provider of predictive technology solutions. Our advanced sensing, software and analytics combined with our engineering experience are deployed on wind turbines around the world to maximise production and make turbines more reliable for longer, optimising energy production.

ONYX Insight is part of the Macquarie Group. Macquarie is a global financial services group operating in 34 markets in asset management, leasing and asset financing, market access, commodity trading, renewables development, specialist advisory services, capital raising and principal investment. The diversity of the Macquarie Group operations combined with a strong capital position and robust risk management framework has contributed to a 54 year-record of unbroken profitability.

ONYX Insight is an equal opportunity employer and values diversity at our company. We do not discriminate based on race, religion, colour, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.