Designing a 1000 Floor Elevator

Designing a 1000-Floor Elevator Panel: A Real Product Management Case in Action

In product management interviews, you’re often asked to design or improve something deceptively simple — but under extreme constraints.

In this Product Management Case Mock Interview Practice session, our mentor Sanket Vaidya asked the candidate a classic design challenge:

“Design an elevator panel for a 1000-floor building.”

Here’s how it unfolded.

The Design Question

Sanket: Do you have a pen and paper handy? Can you see my screen?

Student: Yes, sir.

Sanket: Okay, okay. Go on.

Sanket: Great. You’ve seen regular elevator panels, right, something like I am sharing here. I want you to design an elevator panel for a 1000-floor building. It doesn’t have to be the traditional button-based layout — it can be anything. Sketch something and let’s walk through your design.

Student: Okay. So we can design it however we want? Doesn’t have to follow the image you showed?

Sanket: Yes, anything is fine. It’s a clean slate. Just think about the problem — a thousand floors, multiple users. Design accordingly.

Student: (pauses to sketch) Okay, I’m done. Should I share the picture?

Sanket: Yes. You can either email it, open it on WhatsApp Web, or just share your screen.

Student: (shares screen) Can you see it?

Sanket:Yes, got it. Go ahead and explain.

The Initial Design

Student: So I’ve taken inspiration from our phone’s lock screen. It’s a touchscreen number pad — people can just type the floor number. There’s also a ‘Clear’ button in case they press something wrong. I’ve added icons for Stop, Alarm, and Emergency functions too.

Sanket: Okay. But what if I want to go to the 354th floor, and I type “3”… and then pause for a second? Won’t the system assume I meant floor 3 and start moving?

Student: Ah… yes, that’s a good point. Hmm. We can add a ‘Green’ button to confirm the floor number. So the elevator won’t move unless the user explicitly confirms. That way, it doesn’t respond mid-input.

The Revised Thinking

Student: Actually, let me show you another sketch — I just made an updated version.
In this version, I’ve added that green “Confirm” button more prominently. When someone walks in, they type their number, then hit Confirm. If another person wants to go to a different floor, they can press a different icon (say, “User 2”) and type their number too. The lift then queues both.

Sanket: Okay. But imagine there are 50 people in the lift. How would this design scale?

Student: Hmm. Maybe we can allow them to scroll the screen. But yes, with so many people it could get messy. That’s why I’ve added a “Stop” button — so if someone just wants to get off at the very next floor, they don’t need to type anything. They can just press Stop and exit when it halts next.

Sanket: So the Stop button acts like a “get me off at the next opportunity” feature?

Student: Yes, exactly. Let’s say someone enters on the first floor and needs to get off at the second — they don’t want to interact with the whole panel. Just one tap and done.

Sanket: Alright. But imagine three or four people entering at once — how do they know when to type? Won’t they interfere with each other?

Student: We can segment the interface. Maybe show “User 1,” “User 2,” “User 3,” etc., like tabs. Each person gets a virtual input space. Once confirmed, the system adds all floors to a master queue, optimizing the route.

Sanket: Okay. And what happens if someone types the wrong floor entirely — say, they meant 954 but typed 9540?

Student:We can have input validation — for example, don’t allow more than 4 digits, or limit max value to 1000. And the Clear button resets the input anytime.

Sanket’s Feedback

Sanket: Elevator panel was a product design question — I asked you to design an elevator panel.In general case questions or design questions, you should start with asking qualifying questions. Over here, you should have started with:

“When you say 1000-floor building, is this only one elevator or are we talking about multiple elevators?”
“Is this a residential building or a commercial one?”
“What are the peak times?”
“What is the capacity of each elevator?”

You need to ask questions to zero in on the exact problem, and then start working on the solution. What you started doing is — you just drew a panel and jumped into the solution, without defining the context.

Student:I didn’t realize it was that kind of product question. I thought it was just about designing something.

Sanket: I understand, thats why Practice Interview helps!. This is how product design questions work — it’s not just about jumping to UI. It’s about asking the right questions first.

Student:Yes, this was the first time I saw this kind of question. I didn’t look at it from an estimation or scoping perspective. I will do a lot more mock interviews now.

What This Case Tested & Takeaways for PM Aspirants

This case wasn’t just about building an elevator panel. It tested the candidate’s ability to:

Solve for scale and usability (how do you pick from 1000 options?)
Account for human behavior and error (input delays, multiple users)
Design for different use cases (quick exits, long journeys, corrections)
Think iteratively — one feedback at a time

Product Management Interview Practice

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