Eric Levine elevine

System Design Cheatsheet

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

Basic Steps

Clarify and agree on the scope of the system

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?

Studying for a Tech Interview Sucks, so Here's a Cheat Sheet to Help

This list is meant to be a both a quick guide and reference for further research into these topics. It's basically a summary of that comp sci course you never took or forgot about, so there's no way it can cover everything in depth. It also will be available as a gist on Github for everyone to edit and add to.

Data Structure Basics

###Array ####Definition:

Stores data elements based on an sequential, most commonly 0 based, index.
Based on tuples from set theory.

	using Org.BouncyCastle.Crypto;
	using Org.BouncyCastle.Crypto.Engines;
	using Org.BouncyCastle.Crypto.Modes;
	using Org.BouncyCastle.Crypto.Paddings;
	using Org.BouncyCastle.Crypto.Parameters;
	using Org.BouncyCastle.Security;
	using Org.BouncyCastle.Utilities.Encoders;
	using System;
	using System.Globalization;
	using System.Security.Cryptography;

	private static byte[] AES_Decrypt_block(byte[] cipherText, byte[] Key)
	{
	// Declare the string used to hold the decrypted text.
	byte[] output_buffer = new byte[cipherText.Length];

	using (AesManaged aesAlg = new AesManaged())
	{
	//If CBC, must initialize IV = O_{128}
	//aesAlg.Mode = CipherMode.CBC;
	//aesAlg.IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

	# app/models/ability.rb

	# All front end users are authorized using this class
	class Ability
	include CanCan::Ability

	def initialize(user)
	user \|\|= User.new

	can :read, :all

	/**
	* Simple GridMousePosition control for OpenLayers
	*
	* Due to the design of Proj4js and standard grid systems,
	* this control uses the included usng.js code instead of a standard
	* projection object.
	*
	* Usage:
	*
	* map.addControl(new OpenLayers.Control.GridMousePosition(

	<html>
	<head>
	<title>Animated Sparkline using SVG Path and d3.js</title>
	<script src="http://mbostock.github.com/d3/d3.v2.js"></script>
	<style>
	/* tell the SVG path to be a thin blue line without any area fill */
	path {
	stroke: steelblue;
	stroke-width: 1;
	fill: none;

	gem 'pg'
	group :development do
	gem 'ruby-debug'
	end
	gem 'rake', '~> 0.8.7'
	gem 'devise'
	gem 'oa-oauth', :require => 'omniauth/oauth'
	gem 'omniauth'
	gem 'haml'
	gem 'dynamic_form'