Java Software Engineer (Low Latency)

Vallum Associates; Greater London; On-site; GBP 90,000 - 150,000; Full time

Job summary

Vallum Associates in London is seeking an experienced Java Engineer specializing in high-performance and low-latency systems to join our engineering team. You will design, develop and optimise ultra-low-latency Java applications for performance-critical environments, including real-time financial market workloads.

The role requires deep knowledge of JVM internals, advanced concurrency, memory management, and Linux, with a focus on predictable latency.

Qualifications

• Proven experience designing high-performance Java applications.
• Deep knowledge of JVM internals, GC tuning, and memory management.
• Experience with low-latency, real-time or market-driven systems.

Responsibilities

• Design and develop high-performance, low-latency Java applications.
• Optimise JVM performance including GC, JIT, memory allocation and runtime config.
• Develop concurrent, event-driven and reactive systems for real-time processing.
• Analyse performance using profiling, benchmarking and observability tools.
• Collaborate with infrastructure to optimise CPU, memory, networking and OS.

Skills

Java

Low-latency

High-performance

Concurrency

Memory management

Linux

Profiling

Observability

Event-driven

Reactive

Tools

Aeron

JFR

JMC

async-profiler

perf

Job description

Location: London, UK

About the Role

We are seeking an experienced Java Engineer specialising in high-performance and low-latency systems to join our London-based engineering team.

You will design, develop, and optimise ultra-low-latency, high-throughput Java applications for performance-critical environments, including real-time and financial market-driven systems.

The role requires strong expertise in JVM internals, advanced concurrency, memory management, networking, and Linux, with a focus on achieving predictable and consistently low latency at both application and system levels.

You will work closely with engineering and infrastructure teams to build event-driven and reactive architectures capable of processing high volumes of real-time data with minimal latency.

Key Responsibilities

• Design and develop high-performance, low-latency Java applications with a strong focus on resource efficiency and predictable performance.


• Optimise JVM performance, including Garbage Collection (GC), JIT compilation, memory allocation, and runtime configuration.


• Design and implement concurrent, event-driven, and reactive systems for real-time processing.


• Develop efficient algorithms and data structures for high-throughput, latency-sensitive applications.


• Work with shared memory, memory-mapped files, and inter-process communication (IPC) for performance-critical workloads.


• Analyse application and system performance using profiling, benchmarking, and observability tools.


• Identify and resolve JVM-level, application-level, and system-level performance bottlenecks.


• Collaborate with infrastructure and platform teams on CPU, memory, networking, and operating-system-level optimisation.


• Design systems that meet strict latency, throughput, reliability, and resource-utilisation requirements.


• Support production systems and continuously identify opportunities to improve performance and scalability.


• Ensure solutions meet the requirements of latency-sensitive trading and market-driven environments.


• Strong hands-on expertise in Java and high-performance application development.


• Deep understanding of JVM internals, JVM tuning, memory management, and performance optimisation.


• Strong knowledge of Garbage Collection, JIT compilation, object allocation, and runtime behaviour.


• Proven experience designing concurrent, low-latency, and high-throughput systems.


• Strong understanding of event-driven and reactive architectures.


• Practical knowledge of Java concurrency, lock-free programming, synchronisation, and multithreading.


• Experience with JNI, Java Unsafe, and/or JNR-FFI.


• Solid understanding of CPU architecture, CPU caching, memory models, and shared-memory concepts.


• Strong knowledge of Linux internals and system-level performance optimisation.


• Good understanding of networking protocols, particularly TCP/UDP, and network performance considerations.


• Strong knowledge of algorithms and data structures, with the ability to optimise them for performance-critical workloads.


• Experience troubleshooting complex production performance and latency issues.

Nice to Have

• Experience with Aeron or other high-performance messaging frameworks.


• Experience working on financial markets, electronic trading, algorithmic trading, or high-frequency trading (HFT) systems.


• Experience with native code integration and system-level optimisation.


• Experience with shared-memory or memory-mapped communication.


• Familiarity with Linux performance tools, CPU profiling, and system-level benchmarking.


• Experience with tools such as Java Flight Recorder (JFR), Java Mission Control (JMC), async-profiler, perf, or similar.


• Experience working with real-time market data, pricing, order management, or execution systems.