Senior Software Engineer

Senior C++ Software Engineer Remote (UK) | Full-Time Build Trading Systems Where Microseconds Matter Shape the future of electronic trading at Reactive Markets, the 2026 OTC Trading Platform of the Year (Risk.net). Our platform handles $50+ billion in daily trading volume across FX, Equities and Crypto, connecting more than 40 of the world's leading liquidity providers. Every day, our technology powers mission-critical trading infrastructure where reliability, scalability and performance directly impact financial markets. We're looking for an experienced Senior C++ Software Engineer to join our engineering team and help build systems operating at the limits of performance. This is an opportunity to work on complex distributed systems, ultra-low latency architecture and high-throughput messaging platforms while influencing the technical direction of a rapidly growing business. Why Join Reactive Markets?

• Work on systems processing $50bn+ daily trading volume
• Influence architecture and technical direction
• Modern stack: C++20, Go, Linux, AWS
• Fully remote UK opportunity
• Small, senior engineering team with high autonomy
• Direct ownership from design through production
• Competitive package with comprehensive benefits The Opportunity As a Senior C++ Engineer, you'll play a key role in evolving our award-winning Switchboard trading platform. You'll design, build and optimise performance-critical systems including:
• Pricing and execution engines
• Market data and reference data platforms
• Connectivity gateways and FIX integrations
• High-performance messaging infrastructure
• Low-latency distributed systems
• Cloud-native services running on AWS This is a true ownership role. You'll be involved throughout the entire software lifecycle, from architectural design and implementation through to deployment, observability and production support. Alongside hands-on engineering, you'll help shape technical strategy, mentor teammates and contribute to the standards that underpin a world-class trading platform. What You'll Be Working With
• Modern C++20
• Go
• Linux systems programming
• AWS cloud infrastructure
• Python
• Git & Shell Scripting
• FIX Protocol
• TCP/UDP Networking
• Distributed Systems Architecture Engineering Challenges
• Microsecond-level latency optimisation
• High-throughput messaging systems
• Large-scale market data processing
• Real-time trading infrastructure
• System observability and resilience
• Multi-asset trading workflows What We're Looking For Essential:
• 5+ years of commercial C++ development experience
• Strong Linux systems programming background
• Experience building high-performance or latency-sensitive applications
• Deep understanding of networking and distributed systems
• Strong software design and architectural skills
• Experience owning production systems Nice to Have:
• Go development experience
• Financial markets or trading technology experience
• FIX protocol knowledge
• AWS cloud experience How You Work We're looking for engineers who:
• Take ownership of what they build
• Deliver high-quality code into production
• Thrive in challenging technical environments
• Mentor and support others
• Communicate clearly in a distributed team
• Enjoy solving complex engineering problems
• Continuously improve systems, processes and people around them What You'll Get Competitive Benefits Package:
• 30 days annual leave + bank holidays
• Private medical insurance
• Pension scheme
• Life assurance
• Dental and optical cashback
• Cycle to Work scheme
• Team socials and company off-sites Career Growth:
• Progression to lead roles, performance specialisation, or technical leadership. We invest in people who invest in us
• Exposure to cutting-edge trading technology.
• High levels of ownership and autonomy
• Opportunity to influence a platform used by some of the world's largest financial institutions Remote-First Culture We trust great engineers to do their best work wherever they are. Our remote-first approach prioritises flexibility, collaboration and sustainable working practices without sacrificing technical excellence. Ready to Build at the Edge of What's Possible? Join an award-winning engineering team solving some of the most demanding challenges in electronic trading. Right to Work: Candidates must have the existing right to work in the UK. We are not currently able to offer visa sponsorship for this role. Reasonable Adjustments: If you need any adjustments or support during the application or interview process, please let us know — we're happy to accommodate. Data Protection: By applying, you consent to Reactive Markets processing your personal data for recruitment purposes, in line with our policy . Apply now and help shape the next generation of high-performance trading infrastructure.