Have a System Design Interview coming up? Breeze through the basics and get interview-ready in hours through a selection of hand-picked practice problems.

sys-design.tar.gz

basic

System design interviews play a vital role in hiring software engineers and managers. These interviews test the ability of the candidate to solve problems under different constraints. A candidate’s performance in a system design interview is a significant factor in deciding the hire/no-hire decisions and the level assigned to the incoming candidate.

In this course, you’ll go through a miniature form of our primary course on system design: Grokking Modern System Design Interview for Engineers & Managers. This crash course aims to give you an overall gist of the system designing process using short, easy-to-digest problems. Each design problem of the course can be completed in about 15 minutes, giving you the flexibility to include them in your jam-packed schedules.

System Design Interview Prep Crash Course

# What is a pub-sub system?
**Publish-subscribe messaging**, often known as **pub-sub messaging**, is an asynchronous service-to-service communication method that's popular in serverless and microservices architectures. Messages can be sent asynchronously to different subsystems of a system using the pub-sub system. All the services subscribed to the pub-sub model receive the message that’s pushed into the system.

For example, when Cristiano Ronaldo, a famous athlete, posts on Instagram or shares a Tweet, all of his followers are updated. Here, Cristiano Ronaldo is the publisher, his post or Tweet is the message, and all of his followers are subscribers.

# Motivation

The hardware infrastructure of distributed systems consists of millions of machines. Using a pub-sub system to communicate asynchronously increases scalability. Producers and consumers are disconnected and operate independently, thereby allowing us to scale and develop them separately. The decoupling between components, the producers and consumers, allows greater scalability because adding or removing any component doesn’t affect the other components.

Let's define the requirements for such a system.



# Requirements 

We aim to design a pub-sub system that has the following requirements.


## Functional requirements

Let’s specify the functional requirements of a pub-sub system:


* **Create a #key# topic: A topic is a collection of related events or messages.  #key#:** The producer should be able to create a topic.

* **Write messages:** Producers should be able to write messages to the topic.

* **Subscription:** Consumers should be able to subscribe to the topic to receive messages.

* **Read messages:** The consumer should be able to read messages from the topic. 

* **Specify retention time:** The consumers should be able to specify the retention time after which the message should be deleted from the system.

* **Delete messages:** A message should be deleted from the topic or system after a certain retention period as defined by the user of the system.





Write “Ed, give me the answer.” to get the correct answer.

How you would use a pub-sub system in a chat application?

## Non-functional requirements

We consider the following non-functional requirements when designing a pub-sub system:

* **Scalable:** The system should scale with an increasing number of topics and increasing writing (by producers) and reading (by consumers) load.

* **Available:** The system should be highly available so that producers can add their data and consumers can read data from it anytime.

* **Durability:** The system should be durable. Messages accepted from producers must not be lost and should be delivered to the intended subscribers.

* **Fault tolerance:** Our system should be able to operate in the event of failures.

* **Concurrent:** The system should handle concurrency issues where reading and writing are performed simultaneously.

Learn to design a pub-sub system and its components.

Introduction

Elementary Design Problems

Advanced Design Problems

Concluding Remarks

Design a Pub-Sub

What is a pub-sub system?

Motivation

Requirements

Functional requirements

Non-functional requirements