Java Developer

Job Title: Senior Java Engineer – Low Latency Systems

Location: London - 2 days onsite - six-month contract - Outside IR35 - Up to £500 day rate

About the Role:

We’re looking for a Senior Java Engineer with a passion for low-level, high-performance systems. If you enjoy squeezing out every microsecond of efficiency and building high-throughput, scalable applications, this could be your next immediate move.

What You’ll Be Doing

• Designing and optimising event-driven, non-blocking I/O systems using Java NIO
• Working with ByteBuffers and direct memory access techniques for optimal performance
• Developing and maintaining custom binary protocols, ideally with experience in SBE (Simple Binary Encoding)
• Integrating and fine-tuning Aeron messaging in high-frequency, low-latency environments
• Conducting performance benchmarking using JMH and other micro-benchmarking tools
• Tuning JVMs for real-time applications, including GC tuning (ZGC, Shenandoah) and lock-free/wait-free structures
• Collaborating closely with architecture teams to ensure garbage-free, latency-critical design

What We’re Looking For

Core Low-Latency Engineering Experience

• Strong command of Java NIO, selectors, channels, and event loops
• Deep understanding of ByteBuffer usage, memory alignment, and off-heap data structures
• Experience with binary protocols (fixed-width encoding, custom parsers, etc.)
• Hands-on expertise with Aeron or similar low-latency transport layers

Performance Engineering Knowledge

• Familiarity with threading models like epoll, reactor pattern
• Use of lock-free/wait-free data structures in production
• JVM internals expertise – GC tuning, heap sizing, latency profiling
• Benchmarking experience with JMH, latency histograms, flame graphs

If this sounds like the kind of challenge you're looking for, hit apply or reach out directly for a confidential chat!