Principal Java Engineer – Retail

Principal Java Engineer (Individual Contributor)
6-Month Contract | Outside IR35 | Paddington (3 days/week)

We are partnering with a leading UK retail organisation on a significant payments and platform transformation. We seek a Principal Java Engineer to join as a hands-on individual contributor, playing a pivotal role within a dynamic engineering team.

This technically demanding position centres on designing, building, and scaling high-volume, mission-critical payment systems. You will remain deeply involved in coding while influencing design and technical direction.

The Role

As a Principal Java Engineer, you will design and develop scalable backend services that facilitate secure payment transactions at scale. The environment is modern, cloud-native, and prioritises event-driven architecture and high performance.

Key Responsibilities

• Design and develop backend services using Java (Spring Boot or Micronaut)
• Build systems supporting secure, high-volume payment transactions
• Develop integrations with payment gateways, acquiring banks, and fraud prevention tools
• Operate within event-driven microservices architectures (Kafka)
• Contribute to system design and resolve complex technical challenges
• Write clean, maintainable, and high-quality code

Cloud and DevOps

• Build and maintain cloud-native systems (Azure preferred)
• Utilise Terraform and Kubernetes for infrastructure provisioning and orchestration
• Work with CI/CD pipelines (GitHub Actions)
• Support monitoring, alerting, and system observability

Security and Compliance

• Implement secure coding practises across all services
• Operate within regulated environments (PCI DSS, PSD2, SCA)

Collaboration

• Collaborate closely with engineers, product teams, and stakeholders
• Contribute to technical discussions and promote engineering best practises
• Support quality assurance across testing, delivery, and system reliability

Requirements

• Proven experience as a Senior or Principal Java Engineer in hands-on roles
• Expertise in Java 17+ with Spring Boot or Micronaut frameworks
• Experience with, or willingness to learn, Kotlin
• Strong understanding of Kafka, event-driven systems, and microservices
• Experience with payment systems, including PSPs, fraud prevention, tokenisation, and settlement
• Cloud experience, preferably with Azure
• Hands-on experience with Kubernetes, Terraform, and CI/CD pipelines
• Knowledge of regulated environments (PCI DSS, PSD2, SCA)
• Experience in retail or high-transaction environments is advantageous

What’s on Offer

• Six-month contract outside IR35, with potential extension
• Hybrid working model: three days per week on-site at Paddington
• Opportunity to work on high-scale, business-critical platforms within a leading retail organisation

If you are a proactive engineer who thrives on solving complex problems at scale, particularly within payments or retail, we would welcome your application.

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