Java Software Engineer (Low Latency)

Java Engineer – High-Performance & Low-Latency Systems Location: London, UK Working Model: Hybrid – minimum 3 days per week onsite 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 . Essential Skills & Experience 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 .