Senior Java Engineer - High-Performance Systems

Fynity; Greater London; Hybrid; GBP 90,000 - 120,000; Full time

Benefits offered by this job

Annual 20% bonus

Hybrid work in London

Pension plan

Career progression

Job summary

Fynity Limited in London is seeking a Senior Java Engineer to design and build high‑performance, low‑latency systems for global financial clients. You’ll work on distributed architectures using Java 17+, Spring Boot, and modern CI/CD practices.

You will own development from design to production, collaborate with architects and client teams, implement asynchronous patterns with Kafka, integrate MongoDB, and contribute to code reviews and testing strategies.

Qualifications

• Strong Core Java knowledge and solid software engineering principles.
• Experience with high‑volume, low‑latency or distributed systems.
• Commercial Java experience with Spring/Spring Boot.
• Experience with Kafka or similar messaging platforms.
• No banking background required, but financial services exposure is a plus.

Responsibilities

• Design and develop high‑performance Java applications using modern Java and Spring Boot.
• Build scalable microservices and distributed, event‑driven systems.
• Develop asynchronous and message‑driven applications using Kafka or similar technologies.
• Work with MongoDB and other database technologies across high‑volume platforms.
• Design and develop REST APIs and contribute to wider system design.
• Solve complex engineering challenges around performance, latency, resilience and scalability.
• Collaborate with engineering, architecture and client teams throughout the development lifecycle.
• Take ownership of software from development and testing through to production.
• Contribute to code reviews, technical discussions and engineering best practices.
• Work with automated testing, TDD/BDD and modern CI/CD practices.

Skills

Core Java (Java 17+)

Spring Boot

Kafka

MongoDB

REST APIs

Distributed systems

CI/CD

TDD/BDD

Problem solving

Tools

None

Job description

Senior Java Engineer – High-Performance Systems

Are you an experienced Java Engineer who enjoys building complex, high-performance applications where speed, scalability and reliability really matter?

We're hiring on behalf of a leading technology consultancy that designs and delivers business-critical platforms for some of the world's largest financial institutions.

We're looking for strong, hands-on Java Engineers with experience developing high-volume, low-latency or distributed systems. You could come from Financial Services, FinTech, Telecommunications, Gaming, E-commerce, Travel Technology or another industry where performance and reliability are critical.

You don't need to come from a banking or payments background. Your technical Java engineering experience is what matters most.

You'll join a highly skilled engineering team working on complex, distributed and event-driven platforms, solving challenging problems around performance, resilience and scalability.

This is a hands-on development role, but you'll also have the opportunity to work closely with architects and client teams, understand technical requirements and take solutions through the wider development lifecycle into production.

What you'll be doing

• Designing and developing high-performance applications using modern Java and Spring Boot.
• Building scalable microservices and distributed, event-driven systems.
• Developing asynchronous and message-driven applications using Kafka or similar technologies.
• Working with MongoDB and other database technologies across high-volume platforms.
• Designing and developing REST APIs and contributing to wider system design.
• Solving complex engineering challenges around performance, latency, resilience and scalability.
• Working closely with engineering, architecture and client teams throughout the development lifecycle.
• Taking ownership of software from development and testing through to production.
• Contributing to code reviews, technical discussions and engineering best practices.
• Working with automated testing, TDD/BDD and modern CI/CD practices.

What we're looking for

We're particularly interested in engineers with strong Core Java knowledge and a good understanding of software engineering principles, rather than simply experience working within a Java environment.

Ideally, you'll have:

• Strong commercial Java experience, ideally Java 17 or above.
• A strong understanding of Core Java and its fundamentals.
• Good experience with Spring / Spring Boot and microservices.
• Commercial experience with Kafka or similar messaging and event-driven technologies.
• Experience with MongoDB, another NoSQL database or a strong wider database background.
• Experience building distributed, highly available or low-latency systems.
• Strong experience developing REST APIs and asynchronous applications.
• Good understanding of automated testing, including TDD/BDD.
• Experience with modern CI/CD and software development practices.
• A background developing complex, business-critical applications where performance, reliability and scalability are important.

Previous Financial Services or payments experience would be useful, but is absolutely not essential.

We're equally interested in speaking with engineers from other industries who have worked on technically challenging, high-volume or performance-critical platforms.

What's on offer

• 20% annual bonus.
• Hybrid working, 2 days per week in London.
• Strong pension and wider benefits package.
• Opportunity to work on complex, high-performance technology used by major financial institutions.
• Exposure to large-scale, distributed and event-driven systems.
• A genuinely hands-on engineering environment with a strong focus on technical quality.
• Opportunity to work alongside experienced engineers, architects and client teams.
• Excellent long-term progression within a growing technology consultancy.

If you're a strong Java Engineer who enjoys solving complex technical challenges and building high-performance systems, we'd love to hear from you.