Prince Mishra prince-mishra

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

If there is a change in Model, check if a corresponding Migrations file is committed.

	/*
	Replace "your_schema" with whatever schema is appropriate in your environment.
	It is possible to use "public"... but you shouldn't!
	*/


	/*
	Function to stamp a "modified" timestamp. Adjust the name to suit your environment,
	but that name is hard-coded so it is assumed that you only use _one_ such name.

	#!/bin/bash
	#
	# git-mv-with-history -- move/rename file or folder, with history.
	#
	# Moving a file in git doesn't track history, so the purpose of this
	# utility is best explained from the kernel wiki:
	#
	# Git has a rename command git mv, but that is just for convenience.
	# The effect is indistinguishable from removing the file and adding another
	# with different name and the same content.

	chrome_options = webdriver.ChromeOptions()

	chrome_options.add_argument("--no-sandbox")
	chrome_options.add_argument("--disable-dev-shm-usage")
	chrome_options.add_experimental_option("detach", True)
	chrome_options.add_argument("--disable-infobars")
	chrome_options.headless = True

	chrome_options.add_argument("--single-process")
	chrome_options.add_argument("--remote-debugging-port=9222")

	from pyvirtualdisplay import Display
	from selenium import webdriver

	display = Display(visible=0, size=(800, 600))
	display.start()

	# now Chrome will run in a virtual display.
	# you will not see the browser.
	browser = webdriver.Chrome()
	browser.get('http://www.google.com')

	#!/bin/bash
	#
	# Bash script to setup headless Selenium (uses Xvfb and Chrome)
	# (Tested on Ubuntu 12.04) trying on ubuntu server 14.04

	# Add Google Chrome's repo to sources.list
	echo "deb http://dl.google.com/linux/chrome/deb/ stable main" \| sudo tee -a /etc/apt/sources.list

	# Install Google's public key used for signing packages (e.g. Chrome)
	# (Source: http://www.google.com/linuxrepositories/)

	# https://gist.github.com/4368898
	# Public domain code by anatoly techtonik <[email protected]>
	# AKA Linux `which` and Windows `where`

	import os
	import sys

	def find_executable(executable, path=None):
	"""Find if 'executable' can be run. Looks for it in 'path'
	(string that lists directories separated by 'os.pathsep';

	server {
	listen 80;
	server_name api.test.com;


	location / {

	# Simple requests
	if ($request_method ~* "(GET\|POST)") {
	add_header "Access-Control-Allow-Origin" *;