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.
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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.