Senior Java Developer - Multithreading/caching - sought by leading investment bank based in London - Contract inside IR35 - umbrella Key ResponsibilitiesDevelop and maintain high-performance backend services for complex data processing workloads.Design scalable architectures for large-volume calculations and data pipelines.Work closely with cross-functional teams to define and deliver new features.Ensure optimal performance, quality, and reliability across backend services.Diagnose and resolve performance bottlenecks and defects.Follow best-practice engineering standards, design patterns, and architectural principles.Apply Test-Driven Development (TDD) in day-to-day development.Use static code analysis tools such as SonarQube to maintain clean, high-quality code.Work efficiently with SQL, data joins, and large/complex datasets.Leverage AI tooling to enhance productivity in coding and system design.Required Skills and Experience8+ years'' experience in Java backend development (Java 17+).Degree in Computer Science, Software Engineering, or related field.Strong expertise in Java + Spring Boot / Spring Data / Spring Cloud.Excellent SQL knowledge and experience optimising queries and data models.Strong understanding of in-memory data loading and efficient join strategies.Deep familiarity with Java tooling (Maven/Gradle, testing frameworks, dependency management).Proven experience building data processing or data-intensive applications.Solid understanding of modern architectural p