Requirements of Quora's Design

Requirements

Let’s understand the functional and non-functional requirements below:

Functional requirements

A user should be able to perform the following functionalities:

• Questions and answers: Users can ask questions and give answers. Questions and answers can include images and videos.
• Upvote/downvote and comment: It is possible for users to upvote, downvote, and comment on answers.
• Search: Users should have a search feature to find questions already asked on the platform by other users.
• Recommendation system: A user can view their feed, which includes topics they’re interested in. The feed can also include questions that need answers or answers that interest the reader. The system should facilitate user discovery with a recommender system.
• Ranking answers: We enhance user experience by ranking answers according to their usefulness. The most helpful answer will be ranked highest and listed at the top.

Non-functional requirements

• Scalability: The system should scale well as the number of features and users grow with time. It means that the performance and usability should not be impacted by an increasing number of users.
• Consistency: The design should ensure that different users’ views of the same content should be consistent. In particular, critical content like questions and answers should be the same for any collection of viewers. However, it is not necessary that all users of Quora see a newly posted question, answer, or comment right away.
• Availability: The system should have high availability. This applies to cases where servers receive a large number of concurrent requests.
• Performance: The system should provide a smooth experience to the user without a noticeable delay.

Resource estimation

In this section, we’ll make an estimate about the resource requirements for Quora service. We’ll make assumptions to get a practical and tractable estimate. We’ll estimate the number of servers, the storage, and the bandwidth required to facilitate a large number of users.

Assumptions: It is important to base our estimation on some underlying assumptions. We, therefore, assume the following:

• There are a total of 1 billion users, out of which 300 million are daily active users.
• Assume 15% of questions have an image, and 5% of questions have a video embedded in them. A question cannot have both at the same time.
• We’ll assume an image is estimated to be 250 KBs, and a video is considered 5 MBs.