Grokking the System Design Interview
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Capacity and data size estimations

adam.vaz

Jul 23, 2023

I've been reading through the different design problems and there's no explanation as to where the data size estimates are coming from (maybe I missed something). For example, with the instragram problem. Why is 500m users chosen? Why is 200Kb for the file size chosen? Then, why is 20 bytes chosen for name field and 32 bytes chosen for the email field? Is there a reference somewhere as to why these values are chosen? How do I make these estimations?

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shekhart91 2 years ago

I would suggest take them as variables instead like x for name field and y for email etc. then at interview you can make an assumption about each and compute the size. This also gives flexibility to change the equation at interview time.

On this page

  1. What is Instagram?

Try it yourself

Designing Instagram (video)

  1. Requirements and Goals of the System
  1. Some Design Considerations
  1. Capacity Estimation and Constraints
  1. High Level System Design
  1. Database Schema
  1. Data Size Estimation
  1. Component Design
  1. Reliability and Redundancy
  1. Data Sharding
  1. Ranking and News Feed Generation
  1. News Feed Creation with Sharded Data
  1. Cache and Load balancing