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Mastering Frontend System Design Interviews: A Complete Guide

How Senior Engineers Navigate Complex Scenarios: Tips, Strategies, and Real-World Examples

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šŸŽÆ Typescript Daily Digest section in this newsletter typically includes tips, use cases, features, and basically anything related to typescript. For this weekly edition, we thought to include a frontend system design interview-style content. Please let us know in your feedback if this is good. If yes, we can continue this every week with a new topic. Also, feel free to suggest different topics/content to cover. You can directly reply to this email to provide your feedback or use this link to share your valuable suggestions, feedback, and questions. We will make sure to publish a Q&A section at the end of every week.

Ok, letā€™s dive into this weekly edition article. We will start with covering what has been going on over the last week in the field of typescript and web.

Todayā€™s newsletter is going to be long and certainly exciting. Keep reading ā€¦

šŸ”„ Top 5 TypeScript Highlights (Weekly Edition)

  1. šŸ“¢ New Release Alert: Typescript 5.2-rc is out. Dive into ā€œDecorator Metadataā€, using ā€œNamed and Anonymous tuple elementsā€, ā€œInline variable refactoringā€, and much more ā€¦

  2. šŸŒ Framework Fusion: Project IDX - What if your dev experience was entirely in the cloud? Curious? Join the waitlist.

  3. šŸ”„ Hot on GitHub: The ā€œgenerative_agentsā€ repository in GitHub has been gaining popularity recently. ā€œGenerative Agents: Interactive Simulacra of Human Behaviorā€.

  4. šŸ’Ž Community Gem: Sei is a general-purpose, open-source L1 blockchain offering the best infrastructure for the exchange of digital assets. It heavily uses typescript. Itā€™s trending this week. Check it out!

  5. šŸ—£ļø Debate Rages: TypeScript is surprisingly ok for compilers. - Hmmm! Follow the debate rage here.

šŸŽÆ TypeScript Daily Digest! (Special Edition)

For this weekly special edition, we will cover typical candidate-interviewer interactions that happen during a front-end-system design round. Again, this is mainly for educational purposes as different companies differ in the interview styles. Regardless, this article should give you a high-level perspective of how to approach a ā€œFrontend System design interviewā€ if you are applying for roles like ā€œSenior frontend Engineerā€, ā€œFrontend architectā€, and similar ones.

Before we read further into this article, letā€™s establish some context:

  1. Interviewer - is the one who is interviewing

  2. Candidate - is the one who is attending the interview (specifically the frontend system design round)

  3. Comment - This is just a suggestion on what is the general expectation for each interaction/discussion. We will try to include both Good and Bad parts so that you can be well-informed of some of the expectations.

Since it is a system design interview round, it is the candidate who should be leading the round and not the interviewer. Imagine this way before you attempt any system design round. The aim of this round is not to implement the flawless solution but to demonstrate the considerations that are taken in order to arrive at some solution. Of course, the implementation is important as well but the primary motive is to brainstorm on the design.

Based on my experience interviewing over 200 people in various companies, this is the place where I find most of the candidates lacking experience. Even the candidates who perform remarkably well in the other rounds (like problem-solving, domain rounds, ā€¦) fail to switch their mindsets to view this round from a different angle.

As a candidate, you should understand the difference between problem-solving rounds and design rounds.

ā€œImagine in your day-to-day work, if you are asked to design an ā€œXYZā€ feature and nobody is there to guide/review you, how will you design the feature making sure that that is usable, scalable, performant, secure, extensible, fault-tolerant, modern, ā€¦ā€

Overall, the intention of the design round is to understand the design thinking skills more than your problem-solving skills. Sometimes both go hand-in-hand, but you understand the gist.

Ok, with this in mind, letā€™s cover a mock-styled interview and see how that works out.

Interviewer: Your task today is to design and implement a simplified version of a scheduling tool like Calendly. Here's a basic wireframe.

More often than not, interviewer will not say anything more than this in the beginning.

This is intentionally done to ensure that the candidate spends good amount of time thinking through and asking the clarifying questions before going further deep into the solution.

Candidate: Okay, to start with, I assume this application allows a user to set their available time slots and lets other users book those slots. Is that correct?

Interviewer: Yes, thatā€™s correct.

Comment:
Good: The candidate began by confirming the core functionality of the system, ensuring that they have a clear understanding of what they are designing.
Bad: If the candidate didnā€™t confirm the basic functionality, they could end up making assumptions that lead to a design that doesnā€™t align with the actual requirements. Also, if they immediately start with coding (which happens a lot of times), that is seen as a red flag.

Candidate: Given the nature of the application, I believe responsiveness is key. The application should work smoothly across various devices, including desktops, tablets, and mobile phones. I am thinking of starting with a mobile-first approach for the UI design. Does that align with our target user base?

Interviewer: Yes, a significant portion of our users will likely be using mobile devices.

Comment:
Good: The candidate is considering the user base and device compatibility upfront, which is essential for user experience.
Bad: If the candidate didnā€™t consider the range of devices the application should support, it might lead to a less-than-optimal user experience for some users.

Candidate: Great. For the UI, I am considering a Single Page Application (SPA) approach, likely using React for its virtual DOM and efficient updates. To manage the state, I might use Redux or Context API. What do you think about this approach?

Interviewer: Why did you choose SPA for this? Could you elaborate on that?

Candidate: Sure. A SPA would load the necessary HTML, CSS, and JavaScript once and then dynamically update as the user interacts with the app. This should result in a more fluid user experience, reducing the load times as users navigate through their scheduling settings and view appointments. Itā€™s especially beneficial for a scheduling tool where users might frequently update their availability.

Comment:
Good: The candidate explains the rationale behind choosing SPA, highlighting the user experience benefits, which is essential for a tool with frequent interactions.
Bad: If the candidate didn't explain why they chose a SPA approach, it could appear that they are choosing technologies without considering the implications for the user experience.

Itā€™s important to choose a good framework or library but even more important is to be able to tell why you have made that choice.

Candidate: In terms of performance, Iā€™m considering lazy-loading non-critical assets and components, so that the initial page load is as quick as possible. Additionally, I think employing code splitting and tree shaking would help reduce the size of our JavaScript bundles. What are your thoughts on this?

Comment:
Good: The candidate is proactively considering techniques to optimize the initial page load, which is critical for user retention and engagement.
Bad: If the candidate didnā€™t bring up strategies like lazy-loading, code splitting, or tree shaking, it may suggest a lack of awareness regarding front-end performance optimizations.

Interviewer: Sounds promising. Can you elaborate on how you plan to measure and monitor the performance?

Candidate: Sure. I would use tools like Google Lighthouse, WebPageTest, or custom Real User Monitoring (RUM) to collect performance data. We should monitor metrics like First Contentful Paint (FCP), Time to Interactive (TTI), and Core Web Vitals. This data could be reviewed regularly and used to inform our optimization efforts.

Comment: Good: The candidate is suggesting specific tools and metrics for monitoring performance, indicating a data-driven approach to performance optimization. Bad: If the candidate didnā€™t have a plan for measuring and monitoring performance, it could result in performance regressions going unnoticed.

Talking about performance is very much necessary in any of the frontend system design rounds.

Candidate: Moving to the data layer, considering that we need real-time updates (e.g., when someone books a slot, that slot should be marked as unavailable immediately), I am thinking of using WebSockets or similar technology to push updates to the client.

Interviewer: How would you ensure the security of this real-time data?

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