For effective transactions, it's essential to view the database at a specific point in time. This consistency is made possible by low-level timestamps and logical sessions. Traditionally, long-running queries would acquire data from a single snapshot until yielding, causing the snapshot time to advance with each yield. Local Snapshot Reads modify this approach by retaining the snapshot and locks when yielding, using logical sessions to record and track resources for release upon completion of an operation or transaction. This allows transactions to work from a consistent point in time across the cluster, enabling multi-document operations without the snapshot time advancing.