Yuri ykushch

#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?

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

	# Set variables in .bashrc file

	# don't forget to change your path correctly!

	export GOPATH=$HOME/golang
	export GOROOT=/usr/local/opt/go/libexec
	export PATH=$PATH:$GOPATH/bin
	export PATH=$PATH:$GOROOT/bin

	If:

	- you add and commit with the wrong email address in git, and
	- your remote has a hook set up to prevent you from pushing with the bad address

	Then you need to amend the author of your commit before push can succeed:

	1. fix your email address in git config:

	$ git config user.name "Your Name"

	git branch -m old_branch new_branch # Rename branch locally
	git push origin :old_branch # Delete the old branch
	git push --set-upstream origin new_branch # Push the new branch, set local branch to track the new remote