Software Engineer

Reactive Markets; United Kingdom; Hybrid; GBP 90,000 - 120,000; Full time

Benefits offered by this job

Up to 30 days leave + holidays

Private health insurance

Pension

Life insurance

Dental/optical cashback

Cycle to work

socials and offsites

Job summary

Reactive Markets Limited is seeking a C++ Software Engineer to build low-latency trading infrastructure on Linux. You will work on pricing engines, connectivity gateways, market data and the messaging layer, shipping in production and owning what you ship.

Join a small, senior team that values performance, reliability and rapid iteration. The role offers remote-friendly options with real flexibility, occasional after-hours for production releases, and hands-on development in a fintech

Qualifications

• 3+ years of C++ development on Linux systems programming.
• Experience with performance-sensitive systems including profiling and deterministic behaviour.
• Familiarity with networking fundamentals (TCP/UDP, sockets).
• Python for scripting, testing and tooling; Git and shell.

Responsibilities

• Build low-latency trading infrastructure on Linux (Switchboard).
• Test, deploy and support software in production.
• Own production code and respond to incidents (15-minute acknowledgment).
• Collaborate with senior engineers to ship reliable, high-performance software.

Skills

C++ on Linux

Performance profiling

Networking basics

Python scripting

Git & shell

Go (nice to have)

Job description

C++ Software Engineer, Low-Latency Trading

Write the C++ behind a trading network that handles billions in daily volume, and grow quickly alongside a small, senior team. You will work on pricing engines, connectivity gateways, market data and the messaging layer that ties them together, then own what you ship in production.

About Us

Reactive Markets is the 2026 OTC Trading Platform of the Year (Risk.net). Our network handles over $75 billion in daily trading volumes across FX, Equities, and Cryptocurrency, connecting 60+ of the world's leading liquidity providers.

We build trading systems that operate at the edge of what's technically possible, where nanoseconds matter and a dropped message costs real money. Our engineering team is small, senior, and deeply invested in the craft of building cutting edge, reliable, high-performance systems.

The Role

We are looking for a C++ Software Engineer who wants to build low-latency trading infrastructure on Linux. You will work on the core components of our Switchboard trading platform, alongside senior engineers who review your work and help you grow.

You build it, test it, deploy it, support it in production and improve it. Occasional hours outside the normal working day are needed for production releases, scheduled maintenance windows and Level 3 support during critical incidents. We keep this to a minimum and recognise the commitment.

What You'll Work On

• Modern C++20 on Linux, with Go for microservices and tooling
• Microsecond-level latency optimisation and high-throughput messaging
• Market data and reference data pipelines across multiple asset classes
• FIX protocol integrations with global banks and liquidity providers
• Cloud-native infrastructure on AWS, with colocation in key data centres
• Observability: dashboards, alerting and metrics that make system behaviour visible

What We Need

• 3+ years of strong C++ with Linux systems programming, working close to the metal
• Experience with performance-sensitive systems: profiling, optimisation and deterministic behaviour
• Familiarity with networking fundamentals (TCP/UDP, sockets)
• Python for scripting, testing and tooling; Git and shell
• Nice to have: Go (strong C++ engineers pick it up quickly), and experience in financial services or trading technology

How You Work

• You ship. You iterate, improve and get things into production.
• You own it. You take responsibility for what you build in production, including incident response (15-minute acknowledgement during working hours).
• You care about quality. Clean, testable code and thoughtful peer reviews, without gold-plating.
• You write things down. We are distributed across time zones; if it is not written down, it does not exist.
• You communicate. Clear, proactive communication, especially when things go wrong.
• You use AI tooling. We use Claude and Gemini for code review, debugging, incident investigation and documentation. Curiosity matters more than expertise.

What You Get

• Real problems: performance measured in microseconds, not user clicks
• A small team of senior engineers with clear accountability and direct impact on clients
• Up to 30 days leave plus bank holidays, private health insurance, pension, life insurance, dental/optical cashback, cycle to work, socials and offsites
• Remote-friendly with real flexibility, and a sustainable pace
• Career progression to senior roles, performance specialisation or technical leadership

Our Hiring Process

• Initial conversation with Talent Acquisition (video, 30-45 min)
• Technical interview with two members of the engineering team (video, ~60 min)

Stages 2 and 3 may swap depending on availability. We aim to keep momentum, and feedback typically comes within a few business days.

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.

Equal Opportunities:

Reactive Markets is an equal opportunities employer. We welcome applications from all qualified candidates regardless of age, disability, gender reassignment, marriage or civil partnership, pregnancy or maternity, race, religion or belief, sex, or sexual orientation.

Reasonable Adjustments:

If you need any adjustments or support during the application or interview process, please let us know.

Data Protection:

By applying, you consent to Reactive Markets processing your personal data for recruitment purposes, in line with our privacy policy.

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