Amazon doesn't have an unlimited supply of every item it stocks. And some of the more popular items could easily sell out during Prime Big Deal Days. If you have your eyes on a particular product, you may want to see if you can sign up for an invitation to buy it.

Thanks to the early Prime Big Deal Days sale price, the Fire HD 10 tablet with 64GB of storage is just $99.99 at Amazon, a 44% discount off the usual price of $179.99. The 32GB size is on sale for $89.99, so you'll be scoring twice as much storage capacity for just $10 more.

Amazon Prime Big Deal Days are mega-event sales during which Amazon slashes prices on tens of thousands of popular items. The sale lasts for just two days. Inventory on many products that go on sale is limited, so if you want to get the best deals, shop early to snag the items you want at a deep discount.