Server side encryption

• put request path
• get request path

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Rate limiting

• Token bucket
• Leaking bucket
• Fixed window counter
• Sliding window log
• Sliding window counter

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1-dimension array

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int[] arr = new int[]{ 1, 2, 3 };
int[] arr2 = {1,2,3,4,5};
int len = arr.length; // 3
int len2 = arr2.length; // 5

2-dimension array

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int[][] matrix = {{1, 2}, {3, 4}};

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Pane

• spilt horizontally: Ctrl-b %
• split vertically: Ctrl-b "
• navigate between panes: Ctrl-b <arrow key>
• close: Ctrl-d
• make a pane go full screen: Ctrl-b z
• shrink it back to its previous size: Ctrl-b z again
• resize pane in direction: Ctrl-b esc-<arrow key>

Window

• create new window: Ctrl-b c
• navigate: Ctrl-b p / Ctrl-b n / Ctrl-b <number>
• close: Ctrl-d
• rename: Ctrl-b ,

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Good questions to start

1. What is your role?
2. How long have you been in your current role? What did you do prior to this role?
3. Who is on your team (if applicable)? How do you envision me working with them?

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This article is about the process of defining archiecture, components, modules, interfaces and data for a system to satisfy specified requirement, the structure mainly used for system design interview.

Clarify the problem (Scenario)

Clarify the problem or in another word, scenarios and use cases (include corner cases).
Below is an example for a video streaming service:

• Register/log in, play video, or video recommendation
• Prioritize all the scenarios and deep dive into it.
• Play video
  • (1) Generate channel
  • (2) Get all videos in the channel
  • (3) Play videos in the channel

Requirements include functional and non-functional requirements. non-functional requirements includes: scalability, performance, availability, security.

Due to the limit of time, we should prioritize and identify which ones are critical. and for non-functional, we could discuss some trade-offs. For example, a system highly optimized for read operations might have slower write operations.

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There is a template for binary search, by using which you do not need to think too much about the boundary and how to narrow down the interval / how to calculate mid value.

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// check null …
int s = 0, e = array.size() - 1;
while (s + 1 < e) {
    int mid = s + ((e - s) >> 1);
    if (array[mid] == target) { ... }
    if (array[mid] > target) { e = mid; }
    else { s = mid; }
}
// check value
if (array[s] == target) { ... }
else if (array[e] == target) { ... }

Compared with normal binary search, the difference is that it cannot find the optimum value at while loop, instead, it sustains two possible value, and then check them after loop.

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Questions and answers

The problems are all under: leetcode database section
And my solutions are here: my solution

177 - Nth Highest Salary

For question 177, I need to know how to use mysql function.

1. Delete exists same function
   mysql> drop function if exists getNthHighestSalary;

2. change default delimiter
   Since the default delimiter is ;, change it to ^^
mysql> delimiter ^^

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1. Install HomeBrew

   1	ruby -e "$(curl --insecure -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

2. brew install mysql

3. Start mysql service: mysql.server start

4. Set password: mysql_secure_installation

5. Login: mysql -u root -p

Install scala

1. Download scala-X.XX.tgz from the official site.
2. Unzip archive and move it to /usr/local folder
   If you step into ./bin folder, you could use ./scala to run it.
3. Open your .bash_profile file :
   sudo nano ~/.bash_profile
4. Add scala/bin folder to your PATH
   export PATH=/usr/local/scala/bin:$PATH
   Control + X to save and restart.
5. Check successful by typing Scala in terminal
   If you see below, then Scala is successfully installed.

   1 2	Welcome to Scala 2.12.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_121). Type in expressions for evaluation. Or try :help.

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