Senior Java/FIX Engineer

Who you are

• Substantial commercial experience building backend systems in Java — enough that you've owned services in production, made the architectural calls, and lived with the consequences
• Strong command of concurrency and multi-threading — not just the APIs, but the failure modes, and how to reason about correctness under load
• Real experience with asynchronous and event-driven systems — streaming, messaging or queueing
• Spring Framework in anger, including Spring Boot
• Experience designing and operating externally-facing APIs, where you don't control the client and can't break the contract
• Cloud experience, ideally AWS
• Linux proficiency, including shell scripting
• The analytical instinct to work a hard production problem from symptom to root cause using logs, metrics and traces — and the patience to do it properly rather than guess
• Clear communication with non-engineers. You'll be explaining technical constraints to client-facing teams and business stakeholders regularly

What the job involves

• Our team sits within the IG Prime division, building the institutional side of IG's business. The Prime API team owns the APIs that connect IG to institutional clients, brokers and partners across global markets — the trading and market-data plumbing that our largest clients depend on every trading day. Maintaining and modernising our FIX-based APIs is one of the team's core functions, and it's the area this role would lead on
• That means real-time price distribution, order and execution flow, and reference data, running continuously through the trading day. When these systems degrade, clients notice immediately — so resilience, correctness and latency aren't aspirations here, they're the job
• You'll join at a genuinely interesting point: we're building a new suite of cloud-native trading APIs alongside modernising our existing FIX estate. There's greenfield work and there's hard, high-stakes work on live systems, and you'd get both
• Design and build new trading and market-data APIs — REST, streaming and FIX — used directly by institutional clients
• Modernise IG's FIX offering: bringing our session handling, market-data distribution and order flow up to the standard of the best venues in the industry
• Solve the problems that come with real-time distributed systems in a trading environment — resilience under load, recovery from failure, and correctness in flows where getting it wrong has direct client impact
• Own your services end to end: architecture, implementation, testing, deployment and production behaviour
• Use observability data to understand and improve latency, throughput and reliability — and to find the problems clients haven't reported yet
• Work directly with FIX Support, dealing desks and client-facing teams to diagnose live issues. Client-facing technical support is a real part of the role, and some of the most valuable work we do
• Help shape how the team works, including our move towards spec-driven, AI-assisted development — we're early enough that you'd be influencing the approach rather than inheriting it
• Raise the bar for engineering standards on the team: testing, documentation, and challenging designs that won't hold up