Ankur Anand ankur-anand

Backend Architectures

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ror, scala, jetty, erlang, thrift, mongrel, comet server, my-sql, memchached, varnish, kestrel(mq), starling, gizzard, cassandra, hadoop, vertica, munin, nagios, awstats

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

	/*
	* Authenticate Django users in node.js.
	*
	* Django is great for many projects, while node.js does some fantastic
	* jobs that Django couldn't. For example, you may have a Django app
	* managing your user accounts and another real-time service or application
	* running on Node, then you probably will need to read Django user session
	* to authenticate users in the Node project.
	*
	* This gist is not production ready yet, but it demonstrates how could it

	#!/bin/bash

	# https://gist.github.com/robwierzbowski/5430952/
	# Create and push to a new github repo from the command line.
	# Grabs sensible defaults from the containing folder and `.gitconfig`.
	# Refinements welcome.

	# Gather constant vars
	CURRENTDIR=${PWD##*/}
	GITHUBUSER=$(git config github.user)

	import string

	# 1. Polynomials
	def evaluatePoly(poly, x):
	return float(sum(b * (x ** a) for a,b in enumerate(poly)))

	# 2. Derivatives
	def computeDeriv(poly):
	return [float (a * b) for a, b in enumerate(poly)][1:] or [0.0]