During initial block download, the node’s wallet(s) scans every arriving block looking for data that it owns. This process can be resource-intensive, as it involves sequentially scanning all transactions within each arriving block.
To avoid wasting processing power, we can skip blocks that occurred before the wallet’s creation time, since these blocks are guaranteed not to contain any relevant wallet data.
This has direct implications (an speed improvement) on the underlying blockchain synchronization process as well. The reason is that the validation interface queue is limited to 10 tasks per time. This means that no more than 10 blocks can be waiting for the wallet(s) to be processed while we are synchronizing the chain (activating the best chain to be more precise). Which can be a bottleneck if blocks arrive and are processed faster from the network than what they are processed by the wallet(s).
So, by skipping not relevant blocks in the wallet’s IBD scanning process, we will also improve the chain synchronization time.