Magento has a very complex data architecture. Data is broken down into hundreds of data tables as part of its intent to provide true flexibility and customization. A single product record, for example, may be stored across dozens of tables, each having a distinct purpose of storing a particular aspect of the data that, when combined, comprises the final product to display to your customers.

If Magento had to look up data across all these tables every time someone visited a product detail page, the rendering of the page would be very slow. As your site traffic increases, the slowing down becomes more and more noticeable.

Therefore, in order to provide fewer lookups for each rendered page, Magento indexes the data by combining the data from all the various related tables into only a few tables. This greatly increases the speed of your store.

In Magento 2, this indexing can occur whenever you change a record in your store or automatically according to a timed schedule, which is...