Java jobs in United Kingdom

Visa is a world leader in payments and technology, with over 259 billion payments transactions flowing safely between consumers, merchants, financial institutions, and government entities in more than 200 countries and territories each year. Our mission is to connect the world through the most innovative, convenient, reliable, and secure payments network, enabling individuals, businesses, and economies to thrive while driven by a common purpose – to uplift everyone, everywhere by being the best way to pay and be paid.

Make an impact with a purpose‑driven industry leader. Join us today and experience Life at Visa.

At Featurespace, we strive to be the world's best software company at protecting our clients and their customers from fraud attacks. We do that with personality, heart and professionalism, cultivating an innovative, fun and positive team atmosphere where everybody can contribute to solving our clients' problems in new, innovative ways. We are always seeking to be the best at what we do and make our customers smile.

Our real‑time Financial Fraud Detection platform processes massive volumes of streaming and historical data. To meet our ambitious performance and scalability goals, we are looking for a Senior Software Performance Engineer with deep expertise in JVM tuning, distributed systems optimisation, and AWS infrastructure performance.

In your role as Senior Systems & Software Performance Engineer, you will help us achieve our goals and deliver success on behalf of our customers by:

• Participating in daily stand‑ups and team meetings to synchronise activities with the team, often leading the call to ensure everyone is aligned.
• Setting the standard of performance‑focused engineering, ensuring that our systems are optimised for high throughput and low latency.
• Tackling complex performance challenges and participating on the on‑call out of hours rota to assist support teams with resolutions to customer incidents related to performance issues.
• Profiling applications using JFR, async‑profiler, and JProfiler, and driving code/configuration changes from findings.
• Tuning and scaling our data infrastructure
• Designing cloud architectures optimised for performance and cost
• Building and maintaining sizing calculators for ingestion, storage, and query workloads.
• Defining and validating SLAs/SLOs, implementing observability to track p50–p99.9 latency and throughput.
• Leading performance incident investigations and postmortems.
• Collaborating with cross‑functional teams to deliver high‑performance and reliable solutions.
• Coaching and mentoring other engineers in performance engineering best practices.

As a company we hire people with a willingness to adapt to a variable role, so along with the key responsibilities below, we ask for ownership of any other duties as required.

• Expert understanding of relevant technologies – JVM internals, distributed systems, and Linux performance tools.
• Ability to write optimised, scalable code and leave systems better than you found them.
• Solve complex performance issues and help others debug and resolve bottlenecks.
• Improve system performance through deep analysis and proactive tuning.
• Act as a code approver for performance‑related changes across teams.

• Lead significant performance engineering initiatives and make impactful contributions to system scalability.
• Drive technical improvements, optimisations, and architectural decisions that enhance performance.
• Identify solutions to large‑scale performance issues, collaborating with peers and stakeholders.
• Participate in interviews and recruitment for performance‑focused roles.

• Take full ownership of performance projects and ensure success from design to production.
• Regularly mentor other engineers, especially in profiling, tuning, and scaling.
• Onboard new engineers into performance best practices.
• Provide and seek timely, actionable feedback.
• Promote good engineering practices and help others deepen their knowledge.
• Show confidence in decision‑making and draw on expertise across the company when needed.

This is a hybrid position. Expectation of days in office will be confirmed by your hiring manager.

• A Degree in Computer Science, Engineering, Mathematics, or a related field – or equivalent practical experience
• Proven experience in JVM performance tuning (G1, ZGC, Shenandoah), heap/thread tuning, GC analysis.
• Knowledge of Java profiling tools (JFR, async‑profiler, JProfiler).
• Hands‑on experience with real‑time data streaming (Kafka, RabbitMQ etc), NoSQL databases (MongoDB, Redis) and monitoring (Prometheus, Grafana).
• Proficiency with Linux performance tools.
• Ability to manage and prioritise workload independently.
• Code profiling and performance tuning.

• Experience with relational and/or NoSQL databases for large datasets.
• Experience with modern IDEs, source control, and CI/CD systems.
• Knowledge of performance patterns and trade‑offs in distributed systems.
• Hands on AWS experience
• Experience with scalable distributed applications.
• Familiarity with schema/serialization optimisation (Avro, Protobuf).
• Experience with HTTP/2 and gRPC
• Cloud automation experience (Terraform, Ansible, CDK).
• Kubernetes workload isolation and resource governance.
• Experience building cost/performance models for infrastructure.
• Java Micro Benchmarking experience
• DevOps/SRE mindset

Visa is an EEO Employer. Qualified applicants will receive consideration for employment without regard to race, color, religion, sex, national origin, sexual orientation, gender identity, disability or protected veteran status. Visa will also consider for employment qualified applicants with criminal histories in a manner consistent with EEOC guidelines and applicable local law.