Low Latency Java Engineer

Citigroup Inc.; Greater London; Hybrid; GBP 110,000 - 140,000; Full time

Benefits offered by this job

27 days annual leave

Discretionary bonus

Private Medical Care

Life Insurance

Employee Assistance Program

Pension Plan

Paid Parental Leave

Learning and development resources

Hybrid work up to 2 days per week

Job summary

Citigroup Inc. in London’s technology division is seeking a senior Low Latency Java Engineer to design, implement and optimise high-performance trading systems.

You will work on microservices-based architectures with Java, C++, and Rust, focusing on ultra-fast response times and scalable data handling. Join a specialist team that delivers cutting-edge market tech, mentors engineers, and supports hybrid work.

Qualifications

• Experience in low-latency Java or Rust trading systems.
• Strong knowledge of market data handling and KDB.
• Proven leadership and project delivery skills.
• Excellent communication and ability to mentor juniors.
• Deep understanding of the JVM, Linux, and kernel concepts.

Responsibilities

• Hands-on coding in Java/Rust for low-latency microservices.
• Lead integration of new products and optimize processes.
• Analyze complex business and system processes.
• Provide SME expertise in Java low-latency development.
• Mentor junior developers.

Skills

Java low latency

Algorithmic trading

KDB / Market data

Linux

OpenOnload

Event-sourced microservices

Team leadership

UML diagrams

C++ (nice to have)

TCP/IP networking

Tools

KDB

Solarflare OpenOnload

Job description

Low Latency Java Engineer

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 require a specialist on algorithmic trading systems utilities including but not limited to market data replay and back test/simulation utilities. The HPA organization are a high skilled enablement group of Subject Matter experts - who produce application frameworks and engage with application engineers to enable application Modernisation to over 100 teams across Citi with a concentration on low latency eTrading platforms in Markets Technology.

Responsibilities include (but not limited to):

• 90% hands in the Java or Rust codebase. We build microservices based 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 area of Java low latency development.
• Utilize advanced knowledge of supported main system flows and comprehensive knowledge of multiple areas to achieve technology goals
• Consult with end users to identify system function specifications and incorporate into overall system design
• Influence and negotiate with senior leaders and communicate with external parties
• Happy to work with and educate and support/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 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 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++

This job description provides a high-level review of the types of work performed. Other job-related duties may be assigned as required.

What we’ll provide you

By joining Citi, you will not only be part of a business casual workplace with a hybrid working model (up to 2 days working at home per week), but also receive a competitive base salary (which is annually reviewed), and enjoy a whole host of additional benefits such as:

• 27 days annual leave (plus bank holidays)
• A discretional annual performance related bonus
• Private Medical Care & Life Insurance
• Employee Assistance Program
• Pension Plan
• Paid Parental Leave
• Special discounts for employees, family, and friends
• Access to an array of learning and development resources

Visit ourGlobal Benefitspage to learn more.

Alongside these benefits Citi is committed to ensuring our workplace is where everyone feels comfortable coming to work as their whole self, every day. We want the best talent around the world to be energized to join us, motivated to stay and empowered to thrive.

#LI-AP2

Job Family Group:

Technology

Job Family:

Applications Development

Time Type:

Full time

Most Relevant Skills

Please see the requirements listed above.

Other Relevant Skills

For complementary skills, please see above and/or contact the recruiter.

Citi is an equal opportunity employer, and qualified candidates will receive consideration without regard to their race, color, religion, sex, sexual orientation, gender identity, national origin, disability, status as a protected veteran, or any other characteristic protected by law.

If you are a person with a disability and need a reasonable accommodation to use our search tools and/or apply for a career opportunity review Accessibility at Citi.

View Citi’s EEO Policy Statement and the Know Your Rights poster.