The word system design got pretty popular with software engineers ever since the big guns like Facebook, Google, Palantir added an essential system design round in their interview process. I mean that’s how I came across the term.

Now the obvious question that would pop up in our mind is why the knowledge of large-scale system design so important to these companies? I mean, if a candidate is a pro-coder, has the superpower of writing a O(1) complexity solution to any problem. Is it really necessary for him to have a good knowledge of system design too? Okay, O(1) was a bit of an exaggeration but I think you got the point. We rarely get to design large scale services from the bare bones in our software dev career. Isn’t this too much to expect?

Let’s talk.


Why You Should Master Designing Large Scale Systems?

First off, we will discuss why is system design important for software developers in general. Not for the interviews, not for getting hired. But for your knowledge and career growth or maybe you want to start your own thing, you have a cool idea and want to design a system that would scale to millions of users. How would you do it?

Would you hire an architect or would you design it yourself? Of course, design it yourself. And to design a scalable system wouldn’t the knowledge of web application/software architecture, picking the right technology for your use case come in handy?

Having the knowledge of large-scale system design, in other words, the knowledge of web architecture, software architecture, distributed systems, gives you an edge as a software developer.

In your job when implementing new features or when designing a new module from the bare bones or when trying to scale the platform to deal with the traffic influx, you can make better decisions by applying your system design knowledge & really stand out amongst your peers.

Let me walk you through the process of how software is typically developed from the bare bones & why application design knowledge is super important to the developers.


Significance Of System Design – The Importance Of Getting The Application Architecture Right

The architecture is the base of an application & has to be carefully thought, to avoid any major design changes & code refactoring at a later point in time.

Speaking with experience, you don’t want to delve into re-designing stuff. It eats up your time like a black hole. It has the potential to push your shipping date further down the calendar by months, if not longer. And I won’t even bring up the wastage of engineering & financial resources which is caused due to this.

It also depends on what stage of the development process we hit an impasse due to the hasty decisions taken during the initial design phases. So, before we even touch the code & get our hands dirty, we have to make the underlying architecture right.

A look at the architecture of our app should bring a smile to everyone’s face.

Though software development is an iterative and evolutionary process, we don’t always get things perfect at the first go. Still, this can’t be an excuse for not doing our homework.


An Overview Of The Software Development Process

In the industry, architects, developers and product owners spend a lot of time studying & discussing business requirements. In software engineering jargon, this is known as the Requirement Gathering & Analysis.

Once we are done with the business requirements, we sit down & brainstorm the use cases which we have to implement. This involves figuring out the corner cases as early as possible & fitting the Lego blocks together.

If you’re a fan of documentation, you might also want to write a high-level design document.

Now, we have an understanding of the business requirements, use cases, corner cases and all. It’s time to start the research on picking the right technology stack to implement the use cases.

Proof Of Concept

After we pick the fitting tech stack, we start writing a POC (Proof of Concept)

Why a POC?

A POC helps us get a closer, more hands-on view of the technology & the basic use case implementation. We get an insight into the pros and cons of the tech, performance or other technical limitations if any.

It helps with the learning curve if we’re working with completely new tech, also the non-technical people like the product owners, stakeholders have something concrete to play with & to base their further decisions on.

Now, this is only for an industry scale product. If you are a solo indie developer or a small group, you can always skip the POC part and start with the main code.

So, we showcase the POC to the stakeholders & if everyone is satisfied, we finally get down to creating the main repo & our first dev branch on GitHub, or any other similar code hosting service which the business prefers.

Phew!!

So, by now you would have realized how important it is to get the architecture right for the first time & the knowledge of web architecture to developers.

It shouldn’t be that only if you work for a really long while in the industry you should look into software architecture rather it should be the other way around. As you learn to code, you should keep acquiring the knowledge of architecture.

So, this was about having the knowledge of system design to write your own thing. Now let’s find out what companies are looking for in a candidate during their system design rounds.


System Design Interview Process

What Companies Are Looking For In A Candidate During A System Design Interview Round?

Companies don’t expect us to be an expert in system design. The design discussions are open-ended, there is no perfect answer to a solution, no silver bullet, there always trade-offs involved.

They want to gauge our thought process, they want to understand how we approach a design problem or do we immediately go into panic mode when given a problem that we’ve never seen before.

The problem that is given to us is intentionally underspecified. They want us to trigger a conversation and ask clarification questions on the problem like if there are any constraints, what kind of input the system has to handle, how much traffic should the system expect, traffic patterns and so on.

The interviewer as opposed to looking for a specific solution wants to see how we approach the problem as I already said. And as we proceed with designing a system, we end up having a pretty detailed discussion with the interviewer on many different topics like the scalability strategies, fitting technology, data handling strategies, design choices and so on. During the conversation, the interviewer tries to gauge the breadth and depth we have on the topic.  

We need to take the ownership of the system design process, and the onus is on us to explain it to the interviewer the design choices we make, the database type we pick, if there is really a need for the message queue or any other component in the architecture and so on.   

Companies want to take engineers on board who they can trust to come up with a good solution for a problem without having a lot of supervision. They want engineers who understand the use case and the requirements well and come up with a fitting solution as opposed to being just driven by the buzzwords & the hype in the industry.


Let’s hear what Google has to say about the system design interviews.

Prepare For Your Google Interview – Systems Design


The best way to perform in these interviews is to relax and think of the whole round as a session where you are designing the system for your own startup. Bounce your thoughts off the interviewer. Lead the design process, having a discussion with him.

The knowledge of designing large scale distributed systems is one of the most important skills a software developer should have. I’ve developed numerous applications from the bare bones and the knowledge of the fundamentals has always helped me save time and a serious amount of money.

So, till this point, we talked about why you should master system design. Time to talk about how to master system design?


The Right Way To Educate Yourself On System Design

Most of the resources on the web, that I’ve come across, will tell you Oh!! You have an interview at X Company it will take you a couple of weeks to prepare for the system design interview. No, it won’t. I strongly disagree with that notion.

Designing large scale distributed systems is an art. You can’t learn this in a couple of weeks. Trying to learn everything in a couple of weeks is a sure shot way to fail your interview round. When the interviewer starts to dig deeper into specific components and design strategies, you’ll be standing there with a blank face. If you have a few years of experience in the industry, just the surface level info won’t help you nail that system design interview round.

Okay!! So, what do I do?

Learning software architecture takes time, you have to continually educate yourself over time or you’ll end up overwhelming yourself.

Here are a few good resources that I recommend:

InfoQ is an amazing website to follow high-level architectural stuff.

This Software Architecture subreddit is a good place to discuss software architecture.

You can read the engineering blogs of large-scale internet services like Reddit, Facebook and so on. Just Google “engineering blog of X service”

I write about real-life architectures on this blog.

Here are a couple of popular real-life architecture posts written by me:

YouTube Database – How Does It Store So Many Videos Without Running Out Of Storage Space?

How Does Instagram Store & Search Billions of Images

Zero to Software/Application Architect learning track is a series of four courses that I am writing (2 courses published) with an aim to educate you, step by step, on the domain of software architecture & distributed system design. The learning track takes you right from having no knowledge in it to making you a pro in designing large scale distributed systems like YouTube, Netflix, Google Stadia & so on.

Check out my Zero to Software/Application Architect Learning Track


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