Java Software Developer | Low Latency & FIX Connectivity | Financial Services | London, Hybrid
We’re partnered with a specialist engineering firm known for solving demanding performance challenges across financial markets and technology. Their teams design, build and optimise high-throughput, low-latency systems used by global financial institutions where speed, reliability and precision genuinely matter.
They’re now looking for a Java Software Developer with proven experience building high-performance JVM-based systems, ideally within trading, banking, fintech or front-office financial markets environments.
This role would suit someone with around 4–10 years’ commercial engineering experience who has worked on performance‑critical Java systems and has exposure to FIX Protocol, connectivity, messaging or electronic trading flows.
It’s a hands‑on engineering role for someone who enjoys solving hard technical problems, improving system performance and working close to real‑time trading environments.
Location: London City, Hybrid working
Options: Contract-based, Inside IR35 (there is scope for a permanent option)
Level: Mid to Senior, ideally 4–10 years’ experience
What you’ll be doing:
* Designing, building and maintaining high-performance Java applications used in demanding real‑time systems
* Working on low-latency, high-throughput platforms across financial markets and trading environments
* Supporting and enhancing connectivity across external venues, brokers, trading platforms or counterparties
* Working with FIX Protocol, FIX messages, tags, order flow, execution flow and connectivity issues
* Developing and improving testing, benchmarking and performance validation frameworks
* Identifying and removing bottlenecks through systematic performance analysis
* Working with JVM internals, including garbage collection, threading, concurrency, locking and memory optimisation
* Contributing ideas to improve architecture, speed, scalability and reliability
* Quantifying and documenting measurable performance improvements
* Working across both existing systems and greenfield development projects
* Communicating clearly with technical and non‑technical stakeholders in client‑facing environments
Requirements
* 4–10 years’ commercial software engineering experience within Java-based development
* Proven experience building low‑latency, high‑throughput JVM-based systems
* Strong understanding of JVM internals, including GC, threading, concurrency, locking and performance tuning
* Experience with FIX Protocol, FIX connectivity, message flows, order routing or electronic trading connectivity
* Commercial experience working on performance‑critical Java applications
* Exposure to trading, banking, fintech or wider financial markets environments
* Ability to troubleshoot performance issues and explain technical trade‑offs clearly
* Comfortable working across existing platforms and new‑build projects
* Strong attention to detail and a professional, precise engineering approach
Highly Desirable Experience
* Front‑office trading technology
* Market connectivity, broker connectivity, venue connectivity or exchange connectivity
* Messaging systems, event‑driven architecture or real‑time data flows
* Benchmarking, profiling and performance testing tools
* Consultancy, client‑facing engineering or project‑based delivery environments
* Linux, networking, distributed systems or high‑performance computing concepts
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