Principal Java Software Engineer

Fynity; Greater London; Hybrid; GBP 80,000 - 130,000; Full time

Job summary

A leading FinTech consultancy is seeking a Principal Java Software Engineer to join their high-performing team in London. You'll work on building event-driven systems for real-time payments, utilizing modern Java technologies. This role offers hybrid working and the chance to collaborate with major global banks, making a significant impact in the financial services industry.

Benefits

Hybrid working

Opportunity to collaborate with major global banks

Qualifications

• Strong hands-on experience with Java 11+ (ideally Java 17).
• Experience with event-driven architecture, real-time messaging systems.

Responsibilities

• Design and build scalable, high-availability systems processing millions of transactions.
• Collaborate within Agile teams (Kanban/Scrum).

Skills

Java

Reactive Programming

Agile mindset

Tools

Spring WebFlux

Kafka

AKKA

Job description

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Base pay range

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Practice Lead @ Fynity | Building Architecture and Product teams for leading orgs across the UK & Europe

Principal Java Software Engineer

London (Hybrid – 1–2 days/week onsite)

Join a FinTech Powering the Future of Payments

Are you an experienced Senior/Principal Java Software Engineer who thrives in a fast-paced, agile environment? 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 financial institutions.

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 join 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

• Work with cutting-edge tech on globally impactful systems
• Hybrid working – 1–2 days/week in a London office
• Opportunity to collaborate with major global banks
• Fast-paced, product-led environment where your voice matters

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

Seniority level

• Seniority level

  Mid-Senior level

Employment type

• Employment type

  Full-time

Job function

• Job function

  Information Technology, Engineering, and Other

• Industries

  Financial Services, Banking, and IT Services and IT Consulting

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