A data access layer is a critical component of financial institutions' data infrastructure, ensuring consistent, compliant, and flexible data access across domains. It offers a single entry point to access data across systems, supports scalability and agility, and improves data quality and trust by operationalizing data products and contracts. A well-implemented data access layer complements existing architectures, such as lakehouse architectures, and provides key capabilities including universal source support, flexible query methods, data composition and aggregation, automated validation and monitoring, security and compliance, and observability and monitoring. Implementing a data access layer requires a step-by-step approach, starting with defining the data access strategy, implementing data contracts and products, choosing the right tools, starting small and scaling gradually, and continuously monitoring and optimizing the solution to meet evolving business needs.