Hybrid Principal Engineer - AI-Driven Fintech Modernisation

Stelfox Limited; Ireland; Hybrid; EUR 90,000 - 125,000; Full time

Job summary

Stelfox Limited is partnering with a Cork-based fintech to modernise their product and platform stack. As Principal Engineer / Tech Lead you will decompose legacy monoliths into scalable services, write production code daily, and raise the bar on engineering practices.

You will drive incremental delivery, bridge legacy and modern architectures for enterprise customers, and explore AI-enabled opportunities to accelerate the programme.

Qualifications

• Expert-level experience with .NET/C#, deep understanding of modern patterns (async/await, DI, clean architecture).
• Strong full-stack development with TypeScript/Angular.
• Cloud-native development on Azure. AWS/GCP transferable.
• Database design, optimization, and migration for high-volume systems.
• CI/CD pipelines and automated deployment practices.
• Designing scalable APIs with versioning and backward compatibility.
• Experience implementing testing strategies: unit, integration, end-to-end.
• Large-scale refactoring and modernization approaches (incremental decomposition).

Responsibilities

• Lead the modernisation - decomposing legacy monolith patterns into clean, testable services.
• Write production code daily and review PRs.
• Raise the technical bar with coding standards and testing practices.
• Ship incrementally without big-bang rewrites.
• Bridge legacy and modern for production systems serving enterprise customers.
• Leverage AI to accelerate modernisation and unlock new product capabilities.

Skills

C# / .NET

TypeScript / Angular

Azure Cloud

API Design

CI/CD

Legacy modernization

System architecture

Job description

Stelfox Limited is partnering with a Cork-based fintech to modernise their product and platform stack. As Principal Engineer / Tech Lead you will decompose legacy monoliths into scalable services, write production code daily, and raise the bar on engineering practices.

You will drive incremental delivery, bridge legacy and modern architectures for enterprise customers, and explore AI-enabled opportunities to accelerate the programme.