the interview process went very smoothly, I heard back within a few days regarding whether or not they would hire me, they administer saliva drug tests, which I am unsure if they really uncover anything. They have a couple of employees come in and speak with you about the opportunity

Three rounds of interviews. If you're lucky, you'll do two rounds because two managers in the room are two interviews. Then the final interview is with the warehouse manager. Be on time; I cannot stress that enough, as Costco is a very time-sensitive type of position. You only have a three-minute grace period to clock in at your normal hours. Emphasize that you are very prompt and are ready to work through the probation period.