It’s very important to have a structured approach in a System Design interview. The question asked by the interviewer will most like be unconstrained and with a lot of ambiguity. Also, you’ll probably get around 35-40 minutes to design a system, so time management is essential to covering all the important topics and giving details of the critical components.

Some of the signals the interviewer is trying to get in this section are listed below:

• Organised and structured approach
  • A candidate struggling to understand the problem and make any real progress (even after interviewer’s input) is a red flag.
  • A structured approach involves clarifying the problem statement, listing down the requirements, back-of-the-envelope estimation, giving an overview of the system listing key components and walking through them in a logical order. 
• Ability to drive the interview without hints
  • Successful candidates usually do most of the talking and drive the conversation in the right direction without much prompting. This is even more important for senior candidates.
• Address the main problem
  • It’s imperative to understand the main problem we are trying to solve, after reducing ambiguity and constraining the problem statement by asking clarifying questions.
  • Jumping directly into the design after hearing the question, without asking any clarifying questions, is a red flag.
• Deals with main issues in the problem space
  • While designing the system, you are bound to come across many issues, for example: single points of failure, overloaded servers, stale cache data, etc. Successful candidates usually point out these issues while designing the system and propose a workaround.
  • It’s important to remember that we are building the system for a large-scale organisation, so it’s vital for it to scale well. Talking about this and building the system such that it works for large number of users is necessary, and something the interviewer is assessing.