Starbucks' mobile order and pay system has been bringing some of its busiest locations to a standstill, NBC News reported.
The system lets people order ahead and swoop into a store to pick up their coffee, food or unicorn frappucino. It was so popular in the first quarter of 2017 that store traffic ground to a halt as baristas contended with a wave of orders, prompting some walk-in customers to leave.
In 1,200 Starbucks locations, at least 20 percent of transactions in peak hours came from customers using mobile order and pay, the company said.
So the company has been experimenting with new ways to "more efficiently handle increased demand" from both mobile and walk-in customers during peak hours.