Contract Senior Software Engineer / Data Platform Engineer We are recruiting on behalf of our client for a Senior Software Engineer / Data Platform Engineer to support the ongoing evolution of a large-scale financial data platform. The platform combines long-established enterprise systems and legacy components with modern cloud-based services hosted on AWS. It processes high-volume structured data and supports both internal systems and customer-facing applications. A significant portion of the estate is built on SQL Server, making strong SQL expertise essential. The successful contractor will play a key role in modernising core systems, improving performance and reliability, and enabling scalable next-generation services. This role is suited to engineers comfortable working across both legacy and modern architectures, with strong experience in backend development and API design. Key Responsibilities Develop, optimise, and maintain SQL Server queries, stored procedures, and data-processing logic Improve performance through indexing strategies, query optimisation, and tuning of large datasets Design and build backend services using Python or C# Support and enhance legacy systems, contributing to incremental modernisation initiatives Build and maintain reliable, scalable APIs for internal systems and integrations Work with AWS services (including API Gateway) to support cloud-based architectures Improve platform reliability through automation, monitoring, and operational enhancements Contribute to data processing pipelines, ETL workflows, and system integrations Collaborate with engineers, architects, and product teams across distributed environments Apply AI-assisted development tools (e.g., GitHub Copilot, IDE AI assistants) within workflows Contribute to engineering best practices and continuous platform improvement Essential Skills & Experience 8 years of professional software engineering experience Strong expertise in SQL Server (complex queries, stored procedures, indexing, tuning) Experience working with large relational datasets Strong backend development experience in Python and/or C# Proven experience in AWS environments Experience working with complex enterprise or legacy systems Strong analytical and problem-solving skills Desirable Skills API design and development experience Experience modernising legacy systems Knowledge of data processing pipelines or ETL systems Exposure to financial services or market data environments Experience using AI-assisted development tools (e.g., GitHub Copilot) Strong academic background in Computer Science, Engineering, or related field (or equivalent experience)