Step 1 - Understand the problem and establish design scope

When you ask a question, the interviewer either answers your question directly or asks you to make your assumptions. If the latter happens, write down your assumptions on the whiteboard or paper. You might need them later.

What kind of questions to ask? Ask questions to understand the exact requirements. Here is a list of questions to help you get started: • What specific features are we going to build? • How many users does the product have? • How fast does the company anticipate to scale up? What are the anticipated scales in 3 months, 6 months, and a year? • What is the company’s technology stack? What existing services you might leverage to simplify the design? Example If you are asked to design a news feed system, you want to ask questions that help you clarify the requirements. The conversation between you and the interviewer might look like this:

Candidate: Is this a mobile app? Or a web app? Or both?

Interviewer: Both.

Candidate: What are the most important features for the product?

Interviewer: Ability to make a post and see friends’ news feed.

Candidate: Is the news feed sorted in reverse chronological order or a particular order? The particular order means each post is given a different weight. For instance, posts from your close friends are more important than posts from a group.

Interviewer: To keep things simple, let us assume the feed is sorted by reverse chronological order.

Candidate: How many friends can a user have?

Interviewer: 5000

Candidate: What is the traffic volume?

Interviewer: 10 million daily active users (DAU)

Candidate: Can feed contain images, videos, or just text?

Interviewer: It can contain media files, including both images and videos.

Above are some sample questions that you can ask your interviewer. It is important to understand the requirements and clarify ambiguities