vasanthk

System Design Cheatsheet

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

Basic Steps

1. 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?

jboner

Latency Comparison Numbers (~2012)
----------------------------------
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

sindresorhus

#!/usr/bin/env bash
# MIT © Sindre Sorhus - sindresorhus.com

# git hook to run a command after `git pull` if a specified file was changed
# Run `chmod +x post-merge` to make it executable then put it into `.git/hooks/`.

changed_files="$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)"

check_run() {
	echo "$changed_files" | grep --quiet "$1" && eval "$2"

jimmychu0807

use std::str;

fn main() {
  // -- FROM: vec of chars --
  let src1: Vec<char> = vec!['j','{','"','i','m','m','y','"','}'];
  // to String
  let string1: String = src1.iter().collect::<String>();
  // to str
  let str1: &str = &src1.iter().collect::<String>();
  // to vec of byte

IanColdwater

Mute these words in your settings here: https://twitter.com/settings/muted_keywords

ActivityTweet
generic_activity_highlights
generic_activity_momentsbreaking
RankedOrganicTweet
suggest_activity
suggest_activity_feed
suggest_activity_highlights
suggest_activity_tweet

jdarpinian

///bin/true;COMPILER_OPTIONS="-g -Wall -Wextra --std=c99 -O1 -fsanitize=address,undefined";THIS_FILE="$(cd "$(dirname "$0")"; pwd -P)/$(basename "$0")";OUT_FILE="/tmp/build-cache/$THIS_FILE";mkdir -p "$(dirname "$OUT_FILE")";test "$THIS_FILE" -ot "$OUT_FILE" || $(which clang || which gcc) $COMPILER_OPTIONS -xc "$THIS_FILE" -o "$OUT_FILE" || exit;exec "$OUT_FILE" "$@"
#include <stdio.h>

int main() {
  printf("Hello world!\n");
  return 0;
}

jult

#!/bin/sh

# This script runs every other night at 04:56 CET on a webserver I maintain
# Results are always at: https://jult.net/block.txt ( or https://jult.net/block.txt.gz )
# And much smaller, stripped of BS; https://jult.net/bloc.txt
# For use in Tixati IP filter: https://jult.net/bloc.txt.gz !!!
# And finally a txt file with just the bold IP-ranges: https://jult.net/bl.txt (or https://jult.net/bl.txt.gz )

# Download open block-lists, unpack, filter:
curl -s https://www.iblocklist.com/lists.php | grep -A 2 Bluetack | xargs wget -qO - --limit-rate=500k | gunzip -f | egrep -v '^#' > /tmp/xbp

mandrean

# Instructions for fresh install

$ sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume --daemon
# reboot
$ source /nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh
$ echo 'export NIX_PATH=darwin-config=$HOME/.nixpkgs/darwin-configuration.nix:$HOME/.nix-defexpr/channels${NIX_PATH:+:}$NIX_PATH' | tee -a ~/.zshrc
$ echo 'source $HOME/.nix-profile/etc/profile.d/hm-session-vars.sh' | tee -a ~/.zshrc
$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
$ nix-channel --add https://github.com/LnL7/nix-darwin/archive/master.tar.gz darwin
$ nix-channel --add https://github.com/nix-community/home-manager/archive/master.tar.gz home-manager

KodrAus

Profiling performance

Using perf:

$ perf record -g binary
$ perf script | stackcollapse-perf.pl | rust-unmangle | flamegraph.pl > flame.svg

NOTE: See @GabrielMajeri's comments below about the -g option.

swenson

Author unknown.

1.) Algorithm Complexity: You need to know Big-O. If you struggle with
basic big-O complexity analysis, then you are almost guaranteed not to
get hired.
For more information on Algorithms you can visit:
http://www.topcoder.com/tc?module=Static&d1=tutorials&d2=alg_index

2.) Coding: You should know at least one programming language really
well, and it should preferably be C++ or Java. C# is OK too, since