Principal Java Software Engineer

ZipRecruiter; London; Hybrid; GBP 100,000 - 115,000; Full time

Job summary

A leading payments consultancy in London is seeking a Principal Software Engineer to design and build high-availability systems processing real-time transactions. The ideal candidate has strong Java experience, a solid understanding of Reactive Programming, and thrives in an Agile environment. With a competitive salary of £100,000 – £115,000 and a 20% bonus, this role also offers hybrid working options.

Benefits

20% bonus

Hybrid working

Opportunity to collaborate with global banks

Qualifications

• Strong hands-on experience with Java 11+.
• Solid knowledge of Reactive Programming.
• Experience with event-driven architecture.

Responsibilities

• Design and build scalable, high-availability systems.
• Write clean, testable code using TDD and BDD.
• Contribute to architectural decisions.

Skills

Java 11+

Reactive Programming

Event-driven architecture

Agile mindset

Tools

Spring WebFlux

Kafka

Job description

Job Description

Principal Software Engineer (Java)

London – 1 day a week onsite

Join a FinTech Powering the Future of Payments

Are you a seasoned individual contributor looking for a step up into a senior position within a high-performing team within the world of Banking/Payments? Are you passionate about high-throughput, real-time systems? This is your opportunity to help shape the core technology that powers instant payments for some of the world’s largest Banks.

We’re hiring on behalf of a leading payments consultancy, delivering cutting-edge solutions that integrate seamlessly with bank infrastructure to enable real-time, secure transactions across the globe.

What You’ll Be Doing

You’ll be the focal point of a high-performing engineering team building asynchronous, event-driven systems using modern Java technologies.

• Design and build scalable, high-availability systems processing millions of real-time transactions
• Work with Java 17+, Spring WebFlux, AKKA, Kafka, and more
• Write clean, testable code using TDD and BDD
• Contribute to architectural decisions in a fast-evolving codebase
• Collaborate within Agile teams (Kanban/Scrum)

What You Bring

We’re looking for engineers who are pragmatic, performance-focused, and thrive on solving complex distributed systems problems.

• Strong hands-on experience with Java 11+ (ideally Java 17)
• Solid knowledge of Reactive Programming (e.g., Spring WebFlux, AKKA)
• Experience with event-driven architecture, real-time messaging systems (Kafka, JMS)
• Familiarity with asynchronous request handling, scalability, and system resilience
• Agile mindset, with TDD/BDD and CI/CD experience

Bonus: Background in Banking/Payments is helpful but not required – if you’ve built high-performance, real-time systems, we want to talk to you.

What’s In It for You

• £100,000 – £115,000 base salary (DOE)
• 20% bonus
• Work with cutting-edge tech on globally impactful systems
• Hybrid working – 1 day a week (or more if you’d like!)
• Opportunity to collaborate with major global banks
• Fast-paced, product-led environment where your voice matters

If you're a motivated Senior/Principal/Staff Java Software Engineer ready to tackle complex challenges and deliver meaningful change, hit apply – and shape the future of payments with us.