Starbucks with a staff of 5-7 during peak mornings have a goal of ~40 second drive through times which they routinely achieve, while handling non-drive through customer load as well.

Also drive through includes multiple drinks and food items as well crammed into that 40 or so seconds.

When timing the serial steps of making a drink, it takes about a minute from start to finish, but their process is to batch and pipeline drinks so that they generally handle 3-5x drinks per batch in a pipeline (repeatable beverage routine), and this is for a lone barista pumping out hot beverages. The other 4-5 people are usually on cashier duty, and drive through duty.