Principal Engineer

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 is partnering with a Fintech provider located in Cork City who are going through a product & platform modernisation process as they truly embrace the power of AI-first development to help extend Agentic AI services on top of their existing product line being deployed with leading financial institutions across the U.S market.

We are looking to add a Principal Engineer / Tech Lead to help drive the modernisation and take ownership of the hardest problems - decomposing legacy systems, building modern replacements and ensuring transition happens incrementally.

Your role will:

• Lead the modernisation - decomposing legacy monolithic patterns into clean, testable and maintainable services.
• Write Code daily - you are not in meetings all day, you will be writing production code and reviewing PRs.
• Raise the technical bar - Good coding standards, testing practices and engineering patterns.
• Ship Incrementally - without big-bang rewrites.
• Bridge Legacy & Modern - navigate the reality of a production system serving enterprise customers.
• Leverage AI to accelerate - identify opportunities where agentic capabilities can accelerate the modernisation process or unlock new product capabilities.

Experience & Skills requirement:

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

If this sounds like you above and you want to join a company who are heavily embracing agentic AI moving forward as they modernise their entire product & engineering ecosystem.

Please note, this position is located in Cork with 3 days in office, 2 remote from home, so candidates will need to be either located in or near Cork or be willing to relocate for this opportunity.

Stelfox is fully compliant with GDPR regulations and you can read more in our privacy policy here: https://www.stelfox.com/privacy-policy-gdpr/.

Your shared data will not be disclosed or transferred to a third party data controller or data processor located outside the EEA unless we have obtained your express consent.

We look forward to working with you.