YOUR BRIEF
What to work through
Work through amazon Lockers as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Assign a free locker of the right size at the chosen site when a package ships there
- The driver opens the assigned locker and confirms the drop-off
- The customer gets a pickup code and opens the locker with it
- A package not picked up by its deadline expires and goes back for return
BEFORE YOU START
Constraints to discuss
- One locker never holds two packages: assignment is strongly consistent
- Pickup codes are single use and hard to guess
- A site keeps opening lockers for valid codes through a short network outage
Need a starting point?
Watch for these common gaps as you prepare:
- Checking that a locker is free and reserving it in two steps, so two packages get one locker
- Reservations with no expiry, so missed deliveries hold lockers forever
- Guessable or reusable pickup codes
- Turning it into a class diagram and never reaching the concurrency or the outage
Why this question is in the collection
These sources connect the problem to company interview reports or preparation guides. They do not guarantee what a company will ask you.