Senior Low Latency Engineer in London

Engineer the future of global finance. At Citi, our Tech team doesn’t just support finance – we are helping to redefine it. Every day, $5 trillion crosses through our network. We do business in 180+ countries operating at a scale few can match. From deploying advanced AI to helping shape global markets, we build systems that matter. Look to join a team where your work helps influence economies, your ideas can drive innovation and outcomes, and your growth is backed by mentorship, continuous learning and flexibility with potential hybrid work opportunities. Help solve real-world challenges that touch millions and get the opportunity to build the future of finance with Citi Tech.

What We Do / The Team

This is a senior level position responsible for establishing and implementing new or revised application systems and programs in coordination with the Technology Team. The overall objective of this role is to lead applications systems analysis and programming activities. The role is to provide senior, low-latency systems and application framework engineering (skilled in Java, C++, Rust, KDB, market data, algorithmic trading technology) within the London Based High Performance Architectures (HPA) team. The team requires a specialist on algorithmic trading systems utilities including but not limited to market data replay and back test/simulation utilities. The HPA organization is a highly skilled enablement group of subject matter experts who produce application frameworks and engage with application engineers to enable application modernization to over 100 teams across Citi, with a concentration on low‑latency e‑trading platforms in Markets Technology.

Responsibilities include (but not limited to)

• 90% hands-on in the Java or Rust codebase. We build microservices based on event‑sourcing systems on a low‑latency in‑house framework. Response times in the 10 microsecond to 100 microsecond range.
• Lead integration of functions to meet goals, deploy new products, and enhance processes.
• Analyse complex business processes, system processes, and industry standards to define and develop solutions to high‑level problems.
• Provide world‑class expertise in Java low‑latency development.
• Utilise advanced knowledge of supported main system flows and a comprehensive knowledge of multiple areas to achieve technology goals.
• Consult with end users to identify system function specifications and incorporate them into overall system design.
• Influence and negotiate with senior leaders and communicate with external parties.
• Work with and educate, support, and mentor junior developers and less‑experienced senior Java developers.

Key Skills And Experience Required

• Demonstrated subject matter expert (SME) in area(s) of applications development.
• In‑depth experience with algorithmic trading application development, preferably in a low‑latency environment.
• Detailed comprehension and experience with market data handling and associated technologies (such as time‑series databases e.g. KDB).
• Demonstrated leadership, project management, and development skills.
• Passion for coding excellent, commercial‑grade, mission‑critical Java frameworks based on event‑sourcing microservices.
• Complete knowledge of modern Java, the JVM, the Linux operating system, system calls, and the kernel.
• Knowledge of TCP and other IP‑based network protocol technologies, including hardware accelerated kernel bypass (e.g. Solarflare OpenOnload).
• Performance assessment and targeted tuning.
• Design and architectural elegance.
• Experience in implementing projects.
• Great communicator with high EQ.
• Ability to occasionally produce clear diagrammatic documentation and model key aspects in UML sequence diagrams.
• Relationship and consensus‑building skills.
• Nice to have: Background in C++.

What We’ll Provide You

By joining Citi, you will receive a competitive base salary (annually reviewed) and a whole host of additional benefits, including: 27 days annual leave.