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Strategies for a Scalable Web Application

Scale Up vs Scale Out

Scale Up (Vertical Scaling)

• Add more CPU’s or add faster CPU’s to a single server

Scale Out (Horizontal Scaling)

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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

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export type Node = { id: number; parentId: number }

const nodes: Node[] = [
  { id: 1, parentId: null },
  { id: 2, parentId: 1 },
  { id: 3, parentId: 1 },
  { id: 4, parentId: 2 },
  { id: 5, parentId: 2 },
  { id: 6, parentId: 3 },
  { id: 7, parentId: 3 }

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GeekEast

# init
git init                           # init a repo
git clone <remote_url>             # clone a repo from remote

# commit
git add <filename>                 # add to index/staging area
git add .                          # add all files to staging area
git rm  <filename>                 # remove file from index/staging area
git commit -m "commit message"     # snapshot!

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Why Docker?

• guarantee the software always run in the same way.

Get Started

• build docker build -t sample-node-image .
• run docker run -dp 3000:3000 sample-node-image

Update Source Code

• list: docker ps

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• clean screen: 井+K or Ctrl + L
• similar lookup Property.where("name ilike ?", "%Toormina%")

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Read & Learn

Decorators

Decorator	Entity
@Request(), @Req()	req
@Response(), @Res()*	res
@Next()	next
@Session()	req.session
@Param(key?: string)	req.params / req.params[key]
@Body(key?: string)	req.body / req.body[key]

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VScode

• ERB-VSCode-Snippets
  • pe, pc, pre
• Bootstrap v4 Snippets
  • configre shortcut
  • change language mode cmd + '
  • example: b-form-group
  • or copy ~/.vscode/extensions/zaczero.bootstrap-v4-snippets-1.1.3.snippets to erb.json (configure user snippets in vscode)
• ERB Formatter/Beautify

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Ruby

Inspect

• debugger
• Docs

stock = StockQuote::Stock.quote("fb")
stock.inspect

Nil or?