System Design Interview Questions

Introduction to System Design Interview Questions and Answers

System design is the procedure of defining the elements of a system such as the architecture, components and modules, the various interfaces of those components and the statistics that go through that system. Through the engineering of a logical and effective system, it is intended to satisfy specific requirements and needs of a business or organization. It entails an organized approach to the design of a system. Bottom-Up or Top-Down approach is needed to consider all the related variables of the system. Modeling languages are used by a designer to convey the data and knowledge in a structure of a system that is defined by a compatible set of rules and definitions. The designs can be described in textual or graphical modeling languages.

Some of the examples of graphical modeling languages are:

• Unified Modeling Language (UML): It describes the software both behaviorally and structurally with graphical notation.
• Business Process Modeling Notation (BPMN): It is used for Process Modeling
• Systems Modeling Language (SysML): It is used for systems engineering.
• Flowchart: A symbolic or stepwise depiction of an algorithm.

What should one anticipate in a system design interview?

Such an interview normally starts off with a very open-ended problem such as design your own social network (like Facebook, Twitter). As the discussion progresses, the interviewer will add extra restrictions or assumptions to reduce the scope of the problem.

In order to tackle these questions, things that help you are practice and having a structured approach.

Now, if you are looking for a job which is related to System design then you need to prepare for the 2019 System design Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important System design Interview Questions and Answers which will help you get success in your interview.

In this 2019 System design Interview Questions article, we shall present 10 most important and frequently asked System design Interview questions. These questions are divided into two parts are as follows:

Part 1 –System design InterviewQuestions (Basic)

This first part covers basic System design Interview Questions and Answers

Q1) Design TinyURL or bit.ly (a URL shortening service)?

Answer:
Come up with features that the system should support first. Secondly, come up with the estimated numbers of how scalable the system can be.

While designing a service there are three things to consider:

• API(REST API)- Client’s communication approach with the service along with a load balancer which is the front end of the service.
• Application Layer – worker threads or hosts that take the URL and generate the tiny URL for it and store both of them in the persistence layer.
• Persistence Layer – Database

Things to analyze:

• Generate a unique ID for each URL and generate ID’s at scale since 1000’s of URL shortening requests come every second.
• Service handle redirects.
• Support custom URLs.
• Track click stats
• Delete expired URLs

2) Design YouTube/Netflix (a global video streaming service)?

Answer:
Things to analyze:

• In videos, the service will be storing and transmitting a huge amount of data that a large number of users can watch and share them simultaneously.
• Record statistics about videos, for example, the overall number of views, up-votes/down-votes, etc.
• Adding comments on videos in real-time.

Components:

• OC – Clouds like AWS, OpenConnect which act as a content delivery network.
• Backend – Database
• Client – Any device(Desktop, Android, iPhone) from which you play the video on YouTube/Netflix.

Let us move to the next System Design Interview Questions.

3) Designing Quora/Reddit/HackerNews (a social network + message board service)?

Answer:
Things to analyze:

The people who use the services can share links or post questions. Other users can answer questions or comment on the shared links. So the service should do the following:

• Records stats for each answer e.g. the overall number of views, up-votes/down-votes, etc.
• Users should be in a position to follow other users or topics
• List of top questions on the timeline from all the users and the topics they follow (similar to newsfeed generation).

4) Design Facebook Messenger or WhatsApp (a global chat service)?

Answer:
This is the basic System Design interview questions asked in an interview. Things to analyze:

• Design one on one conversations between users.
• Extending your design to support group chats.
• What can be done when the user is not connected to the internet?
• When to send push notifications?
• How to provide end to end encryption?

Structure:

Client > Load balancer > Nodes > Cache(Redis) > Database(Casandra)

5) Design Search Typeahead(Autocomplete)?

Answer:
Things to analyze:

• Typeahead suggestions to be provided.
• Criteria for choosing the suggestions.
• Does the system need to be realtime?
• Support personalization with the suggestions.
• Queries per second to be handled by the system.
• Amount of data to be stored.

Part 2 – System Design Interview Questions (Advanced)

Let us now have a look at the advanced System Design Interview Questions.

6) Design Dropbox/Google Drive/Google Photos?

Answer:
Things to analyze:

• How to upload/view/search/share files or photos?
• Track permissions for file sharing.
• Allowing multiple users to edit the same document.

7) Design Facebook, Twitter or Instagram?

Answer:
Features to be considered:

• Some of the Twitter/Facebook/Instagram features to be supported.
• Need to support replies to tweets/grouping tweets by conversations.
• Privacy controls around each tweet.
• Supporting trending tweets
• Direct messaging
• Mentions/Tagging

Things to analyze:

• The number of users and traffic to be handled by the system.
• Amount of followers the user has.
• The number of times the tweet has been favorited.

Components required to be designed:

• Newsfeed generation
• Social graph
• Systematic search and storage for posts/tweets.

Let us move to the next System Design Interview Questions.

8) Design a Web Crawler?

Answer:
Scalable service is required that can crawl the entire web and can collect hundreds of millions of web documents.

Things to analyze:

• Finding new web pages.
• Prioritizing web pages that change dynamically.
• Ensuring that the crawler is not boundlessly attached to the same domain.

9) Design Uber:

Answer:
This is the frequently asked System Design interview questions in an interview. Architecture: Monolithic/Micro services(Realtime service, Front-end(Application) and database)

• The backend is servicing the mobile phone traffic and clients connect to the backend over mobile data.
• Clients link to the dispatch system which matches drivers and riders.
• Dispatch is written almost entirely in node.js.
• Maps/ETA: In order for dispatch to make an intelligent choice it is important to get maps and routing data.
• Services: Business logic services mostly written in python.
• Databases: Postgres, Redis, MySQL.

Things to analyze:

• Customer requesting a ride and how to economically match them with the nearby drivers.
• Storing tons of geographical locations for drivers and riders who are always on the move.
• Handling updates to driver locations.

10) Design an API Rate Limiter(Github)?

Answer:
Things to analyze:

• Limiting the number of requests an entity can send to an API within a time window, for example, ten requests per second.
• Rate limiting should work for a scattered setup, as the APIs are reachable through a group of servers.

Recommended Articles

This has been a guide to the list of System Design Interview Questions and Answers so that the candidate can crackdown these System Design Interview Questions easily. Here in this post, we have studied top System Design Interview Questions which are often asked in interviews. You may also look at the following articles to learn more –

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