Design
Elevator Group Control System (Multiple Elevators)
Design a control system that dispatches the optimal elevator among several to serve a hall call, minimizing wait time.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It's the "harder sequel" to the single-elevator question — interviewers use it to see if you can design a dispatch heuristic across multiple cars, a real unsolved-in-general optimization problem.
02 - Where this system exists in the real world
You interact with this design every day.
Otis / Schindler multi-elevator dispatch systems
Skyscraper vertical transportation systems
Smart building traffic optimization
03 - What you'll master
Solve this once. Know it forever.
Design a multi-elevator dispatch heuristic
Model each elevator as an independent state machine
Optimize for average wait time, not just correctness
04 - What you'll design
6 functional · 2 non-functional requirements.
Handle hall calls (up/down) from any floor
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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