Ruben Vicario Gonzalez ruben1

System Design Cheatsheet

Step One: Framing The Problem

Identify the use cases that are in scope
Determine constraints based on scoped use cases

use case : the things your system needs to be do.

constraints : the things your system will have to consider to be able to do stuff

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Sublime Text 2 – Useful Shortcuts (PC)

Loosely ordered with the commands I use most towards the top. Sublime also offer full documentation.

Editing

Ctrl+C	copy current line (if no selection)
Ctrl+X	cut current line (if no selection)
Ctrl+⇧+K	delete line
Ctrl+↩	insert line after

	# Install
	cd <project root>
	touch .git/hooks/pre-commit # create pre-commit file
	chmod +x .git/hooks/pre-commit # make it executable
	# copy pre-commit contents to the file


	# Use
	git commit # will trigger the hook. you might see prettier rules fixed after committing
	git commit --amend -n # after checking prettier changes look good, commit again and skip the hook this time

	{
	"bold_folder_labels": true,
	"caret_extra_bottom": 2,
	"caret_extra_top": 2,
	"caret_extra_width": 3,
	"caret_style": "solid",
	"color_scheme": "Packages/User/SublimeLinter/Oceanic Next (SL).tmTheme",
	"ensure_newline_at_eof_on_save": true,
	"fade_fold_buttons": false,
	"font_size": 15,

	require 'open-uri'
	require 'nokogiri'
	require 'csv'


	url = ''
	doc = Nokogiri::HTML(open(url))

	containers = doc.css('') # -> css selector for container
	str = ''

	// Example 1
	mediator.name = 'Doug';
	mediator.subscribe('nameChange', function(arg){
	console.log(this.name);
	this.name = arg;
	console.log(this.name);
	});

	mediator.publish('nameChange', 'Jorn');

	=Navigating=
	visit('/projects')
	visit(post_comments_path(post))

	=Clicking links and buttons=
	click_link('id-of-link')
	click_link('Link Text')
	click_button('Save')
	click('Link Text') # Click either a link or a button
	click('Button Value')

	// Import node modules
	var Q = require('q');
	var Promise = require('bluebird');
	var GitHubApi = require('github');

	// Instantiate github API.
	// NOTE: This is just used for async demonstration purposes, you can imagine any other async functions through this example
	var github = new GitHubApi({
	version: '3.0.0'
	});