A glitch in how Amazon’s shopping cart system applied discounts during Amazon’s second annual Prime Day allowed some lucky shoppers to receive twice the savings as normal. The glitch stemmed from the fact that purchases made through Amazon’s website received discounts categorised as “Lightning” deals, while purchases made using Alexa, through devices like the Amazon Echo or Amazon Tap, recevied discounts categorised as “Alexa on Prime Day” deals. If discounted products were added to one’s shopping cart using both the Amazon website and Alexa, both types of discounts were applied to the order, resulting in twice the usual savings.

The mishap, well for Amazon at least, seems to be related to Amazon mixing Alexa exclusive deals with regular Prime Day deals for Alexa shoppers. When Alexa exclusive deals first went live at 12:00am on Prime Day, there were several Prime Day deals among the list of Alexa deals that weren’t actually exclusive to Alexa shoppers. Among deals like the Fire HD 10 tablet for $129 and the ecobee3 Smart Thermostat for $170, which could only be purchased at those discounted prices using Alexa, there were regular Prime Day deals, like the Fire TV Stick for $24.99 and the Amazon Echo for $129.99, that were available for all Prime members to buy without needing to use Alexa. When asking Alexa to tell you about exclusive deals, the voice assistant would encourage you to visit the Alexa deals page on Amazon after telling you about a few items on the list. Amazon likely mixed regular Prime Day deals in with Alexa exclusive deals to expose Alexa shoppers to a broader selection of products. If you purchased one of the non-exclusive Prime Day deals using Alexa, the “Alexa on Prime Day” discount type would still be applied to your order, instead of the “Lightning” discount type that customers shopping through Amazon.com on Prime Day received. This is key to why some shoppers received twice the savings.

When you shop with Alexa, products you ask Alexa to purchase appear in the Alexa app in real time. From the app, you have the option to add items to your regular Amazon.com shopping cart as an alternative to completing the purchase through Alexa. On Prime Day, if you added items to your Amazon.com shopping cart using the Alexa app, after having asked Alexa for the item, the “Alexa on Prime Day” discount would also be added to your Amazon.com shopping cart so that the price you saw in your cart matched the price Alexa told you and showed you in the Alexa app.

If you already had an item in your Amazon.com shopping cart with the “Lightning” discount present, and then asked Alexa to add the same items to your cart, or you added them through the Alexa app, the “Alexa on Prime Day” discount was added to your order in addition to the “Lighting” discount, instead of replacing it. This allowed customers to buy items with both the “Lightning” discount and the “Alexa on Prime Day” discount, resulting in twice the savings. Going through the process of first adding Prime Day discounted items to your Amazon.com shopping cart and then adding the same items through Alexa, whether deliberate or unintentional, allowed customers to buy products like the Amazon Fire TV for just $39.99, a savings of 60%, the Fire TV Stick for just $9.99, a savings of 75%, and the Amazon Echo for just $79.99, a savings of 55% off the retail price.

At some point, during the first few hours of Prime Day, it seems Amazon caught on and removed the general Prime Day deals that were mixed in with the list of Alexa exclusive deals. This effectively put an end to the double savings, but not before some lucky shoppers scored the best deals of the day.