Al w0rldart

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?

Filter Queries - Example Use Cases

Here are a few example use cases, these use cases combine filter with other parameters to make useful API queries. The syntax for any of this may change between now, implementation, and release - they're meant as illustrative examples :)

Fetch 3 posts with tags which match 'photo' or 'video' and aren't the post with id 5.

api.posts.browse({filter: "tags:[photo, video] + id:-5", limit="3"});

GET /api/posts?filter=tags%3A%5Bphoto%2Cvideo%5D%2Bid%3A-5&limit=3

Populating Data in KeystoneJS

Keystone's createItems function is a simple but powerful way to populate your database with data.

It can be used to create test fixtures or initialise your database with default content / users / etc.

There's also a shorthand syntax that can be used within update files; if you are using the auto updates feature, any file that exports a create object will automatically be wrapped and the data will be created.

createItems takes two passes at the data it is passed, first creating the items and retaining references by key (if provided) that can be used to populate relationships in the second pass. This makes it easy to create related data without asynchronous nesting (which for data creation sometimes ends up in knots).

There's no shortage of good resources for learning laravel. So instead of the usual introductory tutorial were just gonna learn Laravel by building a project from scratch and that's gonna be a User Management System.

I don't know if my definition of a User Management System is correct but here's my idea of what's it's capable of doing:

Register Roles
Register Users
Update Users

	#!/bin/bash

	# Configuration
	#export DIGITALOCEAN_ACCESS_TOKEN= # Digital Ocean Token (mandatory to provide)
	export DIGITALOCEAN_SIZE=512mb # default
	export DIGITALOCEAN_REGION=nyc3 # default
	export DIGITALOCEAN_PRIVATE_NETWORKING=true # default=false
	#export DIGITALOCEAN_IMAGE="ubuntu-15-04-x64" # default
	# For other settings see defaults in https://docs.docker.com/machine/drivers/digital-ocean/

	#!/bin/bash

	module=$1

	for resource in `terraform show -module-depth=1 \| grep module.${module} \| tr -d ':' \| sed -e 's/module.${module}.//'`; do
	terraform taint -module ${module} ${resource}
	done

	CodeDeploy Trust Role

	This Role is attached to CD Deployment Group or to the CD App when is created.

	In the Inline Policies of the Role must be added a Policy called CodeDeployPolicy as follows:

	{
	"Statement": [
	{
	"Resource": [

	// Usage:
	// Copy and paste all of this into a debug console window of the "Who is Hiring?" comment thread
	// then use as follows:
	//
	// query(term \| [term, term, ...], term \| [term, term, ...], ...)
	//
	// When arguments are in an array then that means an "or" and when they are seperate that means "and"
	//
	// Term is of the format:
	// ((-)text/RegExp) ( '-' means negation )

	from flask import Flask
	from flask.ext.mongoengine import MongoEngine
	from flask.ext.security import Security, MongoEngineUserDatastore, \
	UserMixin, RoleMixin, login_required
	from flask.ext.principal import Permission, RoleNeed


	# Create app
	app = Flask(__name__)
	app.config['DEBUG'] = True

	<?php

	use Behat\Behat\Context\ClosuredContextInterface,
	Behat\Behat\Context\TranslatedContextInterface,
	Behat\Behat\Context\BehatContext,
	Behat\Behat\Exception\PendingException;
	use Behat\Gherkin\Node\PyStringNode,
	Behat\Gherkin\Node\TableNode;

	/**