To improve performance when rendering large igGrid datasets in Ignite UI, use row and column virtualization to render only visible rows and columns, and implement paging or lazy loading with remote data to avoid loading everything at once. Disable unnecessary features like grouping, summaries, or complex templates, keep cell templates lightweight, define columns explicitly with autoGenerateColumns: false, and use batch updates to prevent repeated re-rendering. These strategies reduce memory usage, minimize DOM operations, and significantly enhance grid performance for large datasets.