Prince Mishra prince-mishra

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?

This is a post by Joel Spolsky. The original post is linked at the bottom.

This is such a common question here and elsewhere that I will attempt to write the world's most canonical answer to this question. Hopefully in the future when someone on answers.onstartups asks how to split up the ownership of their new company, you can simply point to this answer.

The most important principle: Fairness, and the perception of fairness, is much more valuable than owning a large stake. Almost everything that can go wrong in a startup will go wrong, and one of the biggest things that can go wrong is huge, angry, shouting matches between the founders as to who worked harder, who owns more, whose idea was it anyway, etc. That is why I would always rather split a new company 50-50 with a friend than insist on owning 60% because "it was my idea," or because "I was more experienced" or anything else. Why? Because if I split the company 60-40, the company is going to fail when we argue ourselves to death. And if you ju

	/*
	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.

	#!/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';

	-- Slash commands

	General
	\c[onnect] [DBNAME\|- [USER]]
	connect to new database (currently "pizzastore")
	\cd [DIR] change the current working directory
	\copyright show PostgreSQL usage and distribution terms
	\encoding [ENCODING]
	show or set client encoding
	\h [NAME] help on syntax of SQL commands, * for all commands

	-- Create a group
	CREATE ROLE readaccess;

	-- Grant access to existing tables
	GRANT USAGE ON SCHEMA public TO readaccess;
	GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;

	-- Grant access to future tables
	ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;

	Latency Comparison Numbers
	--------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD