Week 2 July 14 ~ July 20

Step by Step

A/C: 看Doc 理解各个步骤的真正含义，summarize & 简短总结成关键词 so that可以在每个system里面套用
ETA 8号

TinyURL

A/C: TBD
ETA 10号

Pastebin

A/C: TBD
ETA 12号

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System Design Interviews: A step by step guide

Step 1: Requirements clarifications

搞清楚：
包含哪些功能
包不包括video or photos
only focus on the back-end or both back-end and front-end?

Step 2: System interface definition

目的：
establish the exact contract expected from the system
确保requirements 理解正确

Step 3: Back-of-the-envelope estimation（粗略估计）

问问题 --> estimate ==> will help (later) scaling, LB and caching.

问题example:

• scale (如多少tweets posted, 多少tweets viewed, 多少timeline generation等)
• 多大storage
• network bandwidth --> decide how to manage traffic and balance load among servers

Step 4: Defining data model

identify various entities of the system
--> NoSQL or SQL
What kind of block storage should we use to store photos and videos?

Step 5: High-level design

画block diagram with 5~6 boxes 来表示system的components

Twitter example:

high-level components

并且要：根据A需求，我们要用B来handle。
例子：根据有大量read tweets，我们要用separate servers来handle。

Step 6: Detailed design

选一两个dig deeper。根据interviewer 的feedback 详细解释哪一部分。

应该always提供不同的approches，并且比较他们的pros and cons，并说为什么最后选择这种。考虑tradeoff。

可能涉及：

• database partition
• handle hot user
• optimize (LB, cache, etc.)

Step 7: Identifying and resolving bottlenecks

讨论bottlenect，越多越好，并提供不同approches to mitigate them

• single point failure(single point failure impacts the whole system) （failover?）
• replica?
• monitoring & alerts for performance?