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.

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.

• 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

• 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

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

• 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

• 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

• 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.