Most gift card transactions take less than 10 minutes to complete. However, please keep in mind that all transactions are attended to in a FIFO (First-In-First-Out) order, so the processing time differs.
Also, Store gift cards take a longer time to process (1 - 3 hours). Here is a list of them:
American Express
Best Buy
Foot Locker
JCPenney
Mac
Macy’s
Nike
Nordstrom
Saks Fifth Avenue
Sephora
Target
Vanilla
Visa
Walmart
Walmart Visa
Furthermore, the processing time for gift cards, particularly Apple gift cards, with higher denominations/values, may be longer.