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How to Prepare for System Design Interviews? Concepts, Practice, and Resources

Here’s how I got into FAANG

The Software Engineering job market is on fire! Especially if you have a couple of years of experience under your belt. And in the world of Software Engineering, if you are applying for a Senior Engineer / Lead / Architect / or a more senior role, System Design is the most sought-after skill, and hence one of the most important rounds in the whole process. If you mess this up, nothing else would matter. If you get it right though, you’re looking at a raise of at least tens of thousands of dollars annually.

So how do you ace your system design round? Well, here’s what I did while preparing for my interviews with Facebook, Google, and Amazon, and it worked out rather well. I did end up creating a checklist for myself which got me through most of my rounds, so if you follow a similar path you should be able to come up with something that works for you as well.

Before we get into the details though, what is a system design interview? What do the interviewers really expect from the candidates?

Expectations:

  1. You should be able to design a system that satisfies the requirements given to you and scales well.

  2. Your design should be pluggable and not restrict the addition of new features.

  3. You should be able to compare various alternatives and choose the most optimal one. Things like, which database is the most important, or which protocol should you use, or what’s the best approach to scale a system, etc.

  4. You should know the basics that are relevant from a system design standpoint like:

    1. Load balancers

    2. APIs

    3. Caches

    4. Databases

    5. Network Protocols

    6. Message queues

    7. CDNs

    8. High-level details about ML and Big data

    9. CAP Theorem

    10. Monitoring and analytics


In the past, I have shared the best system design courses and best software design questions and in this article, I will share the step-by-step process to crack System design interviews like concepts, common questions, and resources to master system design concepts. 



How to prepare for System Design Interviews?

There is a simple four-step process to ace any System Design round.

  1. Concepts 

  2. Learn from the tech giants

  3. FAQs

  4. Practice


System Design Concepts

Any system design interview will definitely require you to come up with a basic high-level design for whatever system you are trying to build. There are some components that will be needed for sure. Make a note of these components.


Here are a few - 


Load Balancer -  You cannot have a distributed system without a load balancer to distribute the incoming requests among various nodes. This ensures proper resource utilization and that there is no single point of failure in your system. Here’s how Nginx does it.


Cache -  Most systems have some read-heavy interactions, some information that the user will access frequently but not update as much. It makes sense to cache this information in such a way that it can be easily fetched without the need for a DB lookup. Think low latency. Also, based on your use-case, you might need to store more frequently accessed information or more recently accessed information. So, read up on various eviction policies.


Database - Again, there can be no system without some form of data storage. Whether you want to store files, images, product information, financial transactions or simply dump all the data from various user interactions to run analytics later.


It all needs databases. So read up on it. Find out what matters when you are selecting a database, read about SQL/NoSQL, query patterns, and how CAP theorem might come into play while making tradeoffs.


How to Prepare for System Design Interviews? Concepts, Practice, and Resources



Message queues - Sometimes our system needs to perform some tasks that need to be done but not necessarily immediately, or their outcome does not affect the user’s journey. In such cases, rather than making a service call, and waiting for the response, it makes sense to just write the message to the queue so that it can be executed later.


What if you need to insert information in your database, and bulk insert could be more efficient? It would make sense to just keep track of these inserts in a message queue and perform 1 bulk insert instead of hundreds of 1-to-1 inserts to optimize your resources.


CDN - When your users are distributed geographically, getting your content to them in a reasonable amount of time becomes a real challenge. CDNs allow us to maintain a copy of our data in various data centers located closer to the users’ location to reduce the latency. Here is a short video about how Akamai does it


Analytics and Monitoring - This is something that is needed in every system you create. This is a hidden requirement, no one calls it out in the requirement gathering but every interviewer wants this. User logs in or logs out? Wishlisted an item? Payment failed? It is all the information for us! Anything of importance happens, fire an event and save it in your messaging queue.


You can perform real-time analytics on data or just dump it in a Hadoop cluster to use later. Similarly, if an API call is regularly failing, or if your servers are about to run out of resources, wouldn’t you like to know of it beforehand?


Network Protocols - Based on your requirement, based on the type of content you are sharing, you might need to make a decision on which network protocol to use. Read up on various network protocols and when are they relevant, what might be the compromises you might need to make, etc. 


The first step is to know about all these concepts. And by knowing concepts, I don’t mean just some theoretical knowledge of what these are, but more practical hands-on experience about what should be used when.


You need to know things like:

  1. Which is the best alternative to choose from, given the use-case.

  2. What are the tradeoffs that you need to consider while making these decisions?

  3. Best practices for certain use-cases.


To know most of these things, I’ll recommend going through this course on System Design by CodeKarle, which covers all of the above with concrete examples from the real world.


How to prepare for system design interview


Learn from the tech giants

This is probably not going to help in the short term. But in the long term, to become an expert in System Design, it’s best to look at the Tech blogs of various tech companies and see how they are solving various technical problems.


This would paint a clear picture of the real problems that they face and how innovatively they solve them.  Understanding these things would help you become better at system design and also keep you up to date with the latest innovations in tech.


Some of the best blogs to follow are:

  1. Facebook engineering blog

  2. Netflix tech blog

  3. Uber engineering blog




Frequently asked System Design questions

An obvious way to get started with your interview prep! Knowing the basics is definitely important, but it won’t be enough! The most basic way to get started with your practice is to look at some frequently asked questions and their solutions.

Most system design interviews revolve around some 5-6 commonly asked System design questions and if you know the solutions to those, you are more than likely to clear this interview.

The most common questions are:

  1. Tinyurl System Design

  2. Twitter System Design

  3. Facebook System Design

  4. Whatsapp System Design

  5. Airbnb System Design

  6. Uber System Design

If you need resources to solve these questions, something which not only solves the question but also explains the underlying concepts and approach to solving system design questions then this highly-rated course by CodeKarle discusses most of these case studies and some more problems, which has helped many people crack their interviews for companies like Google, Facebook, Microsoft, Amazon, etc.



Practice

Practice, practice, practice! Did I say practice? There are a lot of resources out there. I have shared a few that discuss some of the most popular system design problems in detail. Once you go through a few of them you will start noticing a pattern and will soon be able to come up with solutions on your own.


Get a better understanding of how your systems are designed in your organization. How are the other teams doing things? What factors do they take into consideration? The next best thing is to practice with a friend. Make sure you go through a few mock interviews before your actual interview to avoid some common but easily avoidable pitfalls.


Some most common mistakes that I have seen people make are:


  1. Not driving the interview

  2. Not asking questions

  3. Not structuring the interview properly

  4. Running out of time

  5. Not considering the requirements

  6. Not exploring all the alternate design options

All these mistakes can be easily avoided by having a few mock interviews with someone who knows System Design well. And time your interviews. The target must be to reach a solution within 40 minutes, including time for some discussion.


Well, that’s it, folks. With this 4 step process, you’ll soon be ready to ace any of your system design interviews! Hopefully, this should be a good starting point for you. Happy learning!


System Design Interview Resources

If you need more resources to prepare for the System design Interview here are my recommendations:


Thanks for reading this article so far. If you like this System design interview preparation article then please share it with your friends and colleagues who are preparing for tech interviews. If you have any questions or feedback then please drop a note.

All the best with your interviews.

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