CHAPTER 4: DESIGN A RATE LIMITER 设计速率限制器
In a network system, a rate limiter is used to control the rate of traffic sent by a client or a service. In the HTTP world, a rate limiter limits the number of client requests allowed to be sent over a specified period. If the API request count exceeds the threshold defined by the rate limiter, all the excess calls are blocked. Here are a few examples: • A user can write no more than 2 posts per second. • You can create a maximum of 10 accounts per day from the same IP address. • You can claim rewards no more than 5 times per week from the same device.
CHAPTER 3: A FRAMEWORK FOR SYSTEM DESIGN INTERVIEWS 系统设计访谈的框架
You have just landed a coveted on-site interview at your dream company. The hiring coordinator sends you a schedule for that day. Scanning down the list, you feel pretty good about it until your eyes land on this interview session - System Design Interview. System design interviews are often intimidating. It could be as vague as “designing a wellknown product X?”. The questions are ambiguous and seem unreasonably broad. Your weariness is understandable. After all, how could anyone design a popular product in an hour that has taken hundreds if not thousands of engineers to build?
CHAPTER 2: BACK-OF-THE-ENVELOPE ESTIMATION 粗略估计
In a system design interview, sometimes you are asked to estimate system capacity or performance requirements using a back-of-the-envelope estimation. According to Jeff Dean, Google Senior Fellow, “back-of-the-envelope calculations are estimates you create using a combination of thought experiments and common performance numbers to get a good feel for which designs will meet your requirements” [1]. You need to have a good sense of scalability basics to effectively carry out back-of-theenvelope estimation. The following concepts should be well understood: power of two [2], latency numbers every programmer should know, and availability numbers.
