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System Design Interview An Insider's Guide Volu...

I've come across the book System Design Interview: an Insider's Guide by accident (paperback book, and online course). I was looking for good book resources after several people have been asking me how they can get better at building distributed systems or learning designing systems at scale. Especially when they don't have the opportunity to do so as part of their day-to-day work.

System Design Interview An Insider's Guide Volu...


The topic is somewhat a chicken-and-egg one. You'll know how to design a large system after you designed one before. But if you've not done so: how would you build an URL shortener like, with hundreds of millions of links? A chat app like Whatsapp? A file storage system like Dropbox or Google Drive?

This book is the most "real-world" systems design book I've come across that does a solid effort to teach concepts, step by step, to people who have yet to work at systems at scale. And it's also a welcome refresher to those who are familiar with some of these systems but would like to venture into various other types of large systems. It is clear from the start that the book was written by someone familiar with systems at scale. The author is Alex Xu, a software engineer previously at Oracle, Zynga, and Twitter.

The book lays out time allocation suggestions for an hour-long interview: a few minutes for understanding, 10-15 for the high-level design, 10-25 for the deepdive, and a few more for the wrap-up. I wouldn't be overly prescriptive, but I would suggest to not start the deepdive the first 10 minutes (gather enough context), and leave time for the wrap-up.

One thing you should avoid is "just memorizing" the approaches of the problems. That's far from the point. I made this mistake when I interviewed at Facebook, and was asked to build a part of Instagram. I had done this exercise, and so I just drew out a complicated system. I never talked about constraints or tradeoffs with my interviewer. In fact, I never had a two-way conversation.

A systems design interview is as much about communication with the interviewer as it is about your systems and architecture knowledge. This is why, while the book will help fill gaps you might have on how large systems are built, it won't substitute you collaborating with someone in designing a system.

This book is a solid recommend from me: and not just for preparing for the systems design interview, but to strengthen your systems design muscle for the day-to-day. The book/course comes with typical design problems and brings a pretty good, step-by-step approach to them. But if you just read through them, you'll miss out on the real value of such a resource.

Aim to draw out how you would design the system before reading how the author tackled the problem. You'll go through the book slower: but the concepts will stick. And you'll have approaches to use not just on the interview but when debating with colleagues on how to build a system.

Additionally, the book focuses on backend systems design. Client-side systems design problems for native mobile engineers or web engineers are usually different - I've helped design both these types of interviews. In all fairness, covering those approaches is likely out of scope for this book. Still, for non-backend engineers, the book can be helpful but potentially less applicable.

The book contains 13 original and in-depth systems design challenges not covered anywhere else. These include building a proximity service, a nearby friends feature, Google Maps, distributed messaging queue, metrics monitoring and alerting, a hotel reservation system, real-time gaming leaderboard, digital wallet, stock exchange and more.

In this chapter, we design a payment system. E-commerce has exploded in popularity across the world in recent years. What makes every transaction possible is a payment system running behind the scenes. A reliable, scalable, and flexible payment system is essential.

The system needs to process 1 million transactions per day, which is 1,000,000 transactions / 10^5 seconds = 10 transactions per second (TPS). 10 TPS is not a big number for a typical database, which means the focus of this system design interview is on how to correctly handle payment transactions, rather than aiming for high throughput.

There is a very important design principle in the ledger system: the double-entry principle (also called double-entry accounting/bookkeeping [6]). Double-entry system is fundamental to any payment system and is key to accurate bookkeeping. It records every payment transaction into two separate ledger accounts with the same amount. One account is debited and the other is credited with the same amount (Table 5).

One of the most serious problems a payment system can have is to double charge a customer. It is important to guarantee in our design that the payment system executes a payment order exactly-once [16].

A payment system can mean very different things to different people. Some may think it\u2019s a digital wallet like Apple Pay or Google Pay. Others may think it\u2019s a backend system that handles payments such as PayPal or Stripe. It is very important to determine the exact requirements at the beginning of the interview. These are some questions you can ask the interviewer:

Generally speaking, synchronous communication is simpler in design, but it doesn\u2019t allow services to be autonomous. As the dependency graph grows, the overall performance suffers. Asynchronous communication trades design simplicity and consistency for scalability and failure resilience. For a large-scale payment system with complex business logic and a large number of third-party dependencies, asynchronous communication is a better choice.

The State of Utah has promulgated several regulations governing water reuse. This includes regulations related to approvals and permits for water reuse projects, system design requirements, aquifer recharge, and graywater systems.

Guidelines for the Reuse of Graywater: These guidelines detail the acceptable uses of graywater, including discharge from showers, bathtubs, hand-washing lavatories, and washing machines, as well as considerations for design and system maintenance.

Texas has the third highest reclaimed water flows in the country behind California and Florida. Water reuse goals are published under the State Water Plan, which is updated every five years to provide a new 50 year projection. Texas estimates that water reuse will account for 15 percent of the water supply in the coming decades. The first guidelines for water reuse were passed in 1997 and updated in 2009. There are two categories of non-potable reclaimed water (Type I and Type II) based on whether the water is appropriate for public contact or not. The Texas Administrative Code also includes regulations for the use of graywater and some alternative sources in onsite or decentralized reuse systems. There are no specific water quality standards for potable reuse and therefore these projects are approved on a case by case basis. 041b061a72


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