Ensuring data integrity throughout a pipeline requires the careful selection of data monitors tailored to each stage of the data lifecycle. By adopting shift-left practices, which involve early testing and validation, issues can be identified and resolved sooner, optimizing the efficiency of data migrations and maintenance. A critical aspect of this process is ensuring data parity between systems during migrations or replications, such as moving data from a legacy system to a cloud warehouse. Data Diff Monitors are highlighted as a key tool in this context, providing granular, value-level comparisons to detect discrepancies between datasets, thus enabling real-time resolution of issues. These monitors are essential for achieving a smooth and error-free migration, as they allow teams to verify data alignment continuously, especially during strategies like double-writing, where data is temporarily maintained in both old and new systems. The use of Data Diff Monitors ensures that discrepancies are addressed promptly, facilitating a confident and seamless transition from legacy to new systems.