Senior Software Engineer - Inside IR35 - London

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)