Onboarding & Client Services Associate

Reactive Markets is the 2026 OTC Trading Platform of the Year (Risk.net). Our network handles billions in daily trading volumes across FX, Equities, and Cryptocurrency, connecting 35+ 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 reliable, high-performance systems.

We are seeking a motivated and technically skilled Onboarding and Client Services Associate to join our London team. This role will focus on FIX client onboarding, integrations, and client service delivery across FX, equities and digital assets. The successful candidate will work closely with clients and internal teams to ensure seamless connectivity, smooth integration, and exceptional service throughout the client lifecycle.

What You’ll Work On

• FIX Onboarding & Integrations
  • Lead and manage FIX client onboarding projects — from initial requirements gathering through certification and production go-live.
  • Configure, test, and validate FIX sessions, including order routing, execution reporting, and market data flows.
  • Coordinate conformance testing and certification with clients to ensure compliance with platform standards.
  • Document onboarding procedures, client configurations, and integration best practices.
  • Leverage internal AI and automation tools to streamline client onboarding and troubleshooting.
  • Collaborate with engineering and product teams to support new FIX workflows, APIs, and client integration initiatives.
• Client Services
  • Serve as a frontline technical support for clients in EMEA across FX and equities business lines.
  • Build and maintain strong client relationships, ensuring timely and transparent communication addressing their needs and queries with professionalism and efficiency.
  • Provide ongoing technical and operational support for production trading environments.
  • Manage client inquiries, troubleshoot workflow or configuration issues, and coordinate resolutions across internal teams.
  • Partner with account management, sales and product teams to ensure a positive client experience and successful delivery of platform enhancements.

What We Need

• 3+ years of experience in a client onboarding, integration, or technical support role within a financial technology, trading, or brokerage environment.
• Strong working knowledge of the FIX protocol — message structures, session management, and common trading workflows.
• Proven experience troubleshooting FIX connectivity, analysing logs, and resolving integration issues.
• Familiarity with FX and Equities trading environments, order lifecycle management, and market data connectivity.
• Comfortable with (or curious about) automation and AI-assisted tooling in an operational context.
• Excellent communication and organisational skills, with strong attention to detail and the ability to manage multiple onboarding/client projects in parallel.

Nice-to-have:

• Experience with OMS/EMS platforms, liquidity aggregators, or trading system integrations.
• Exposure to other API protocols and architectures (REST, WebSocket).
• Scripting or automation experience (e.g. Python) and familiarity with monitoring tools (Splunk, Grafana, or similar).
• Understanding of financial market structure and post-trade workflows.

What You Get

• A genuinely rich API to work with — not a thin FIX wrapper bolted onto a legacy system.
• Breadth across FX, Equities, and digital assets.
• Real ownership of the tech-to-business bridge.
• A genuinely tech-first operation.
• A small, senior team.
• Growth across the business.
• Competitive package — up to 30 days leave + bank holidays, private health insurance, pension, life insurance, dental/optical cashback, cycle to work, socials and offsites.

Our Hiring Process

• Stage 1: Initial Conversation with Talent Acquisition - Video call, ~30-45 minutes.
• Stage 2: Team Conversation with one or two members of the Client Services team - Video call or In-person, interactive session, ~60 minutes.
• Stage 3: Leadership Conversation with CRO - Video call or In-person, ~60 minutes.

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 — 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 privacy policy.