Here’s a random lame example:

Take an Invoices table with a child table of line items. The line items has Price_Shipped_Extended, which is the unstored final price of each line item record. (something like: (Qty *Round(Wholesale * (1 – Discount); 2)). When a yearly report on a  particular item or account is run, given a few hundred thousand line items, it will be slow to total up. The fix is conceptually simple: make Price_Shipped_Extended a stored value. Let's say I tried, and FileMaker won't let me store it. I realize that "Wholesale" is simply the price from the Products table being pipelined directly into line items. The fix in that case is to make a new "Wholesale" field in the line items file, and copy the price from the products table when the line item record is created, or at the time a product is entered in. Since the price (and Qty and discount) are now stored values, the extended price can now also be stored, for possibly a 10X speedup in reporting time.