System Design: Instagram

What is Instagram?

Instagram is a free social networking application that allows users to upload photos and short videos. Users can add a caption for each post and utilize hashtags or location-based geotags to index them and make them searchable within the application.Posts appear in a user’s followers’ newsfeeds, and content tagged with hashtags or geotags can be accessed by the broader public, helping users reach a wider audience. Users can also choose to make their profile private, which limits access to those who have chosen to follow them.

Note: As Instagram's user base grows globally, the demand for resources such as servers, databases, and content delivery networks (CDNs) also increases. Instagram must continously optimize its backend architecture to meet the increasing demands of millions of daily active users. Efficiently managing user growth, predicting future resouce requirements, and ensuring scalability are essential for handling the massive volumes of real-time, user generated content.

The expansion in the number of users requires more resources (servers, databases, and so on) over time. Knowing the users’ growth rate helps us predict the resources to scale our system accordingly. The following illustration shows the Instagram user base in different countries as of January 2022 (source: Statista).

How will we design Instagram?

This section is designed for aspiring software engineers or those preparing for system design interviews. We have divided the design of Instagram into four lessons:

1. Requirements: This lesson will put forth the functional and nonfunctional requirements of Instagram. It will also estimate the resources required to achieve these requirements.

2. Design: This lesson will explain the workflow and usage of each component, its high-level design, API design and database schema.

3. Detailed design: In this lesson, we’ll explore the components of our Instagram design in detail, discuss various approaches to generating timelines, and evaluate our proposed design.

4. Quiz: This lesson will test our understanding of the Instagram design.

Let’s start by understanding the requirements for designing our Instagram system, using practical insights on distributed systems and API optimization. In the next lesson, we will provide resource estimations.