Building Performant API's with Koa.js

Tryshchenko Oleksandr @ DataArt
tryshchenko.com || otry.eu

Agenda

• WTF is Koa
• Performant API's with Koa?

"Hey, guys, let's try koa?"

Koa

Express

Overall

Overall

Contributions

What is Koa

So, why Koa? 💡

Event Loop

console.log(1);
setTimeout(() => console.log(2), 0);
console.log(3);

// 1
// 3
// 2

Async

const chownCallback = () => ...;
fs.chown(path, uid, gid, chownCallback);

Sync

fs.chownSync(path, uid, gid);
/** some logic after chown */

Async

• Callbacks
• Promises
• Generators
• Async / Await
• Observables

Async

• Callbacks
• Promises
• Generators (koa.js 1)
• Async / Await (koa.js 2)
• Observables

Async / Await

Async / Await

fetch('https://someapi.somedomain/something')
    .then(response => response.json())
    .then(json => console.log(json));

Async / Await

const res = await fetch('https://someapi.somedomain/something');
const json = await res.json();
console.log(json);

Middlewares

• Context
• Callback

Middlewares

Middleware Architecture

• Shared Context
• Encapsulated request/response
• Synchronous Execution (Cascading)

Scaffold

const Koa = require('koa');
const app = new Koa();

app.use(async ctx => {
  ctx.body = 'Hello Hannover!';
});

app.listen(3000);

Middleware

const Koa = require('koa');
const app = new Koa();

app.use(async (ctx, next) => {
  const res = await nextElections();
  ctx.body = res;
  ...
  await next();
});

app.listen(3000);

Writing a middleware

(ctx, next) => {}

What to take care about

• Concurrency
• Database
• HTTP

Libs Quality

Express?

• Incompatible API's
• Existing libraries "adapters"
• Simple process of porting

Performance isn't about tools...

Performance: Databases

• Use cache for database layer
• Optimize your DB requests
• Take care about DB itself

Performance: HTTP

• Cache answers for frequent requests
• Do complicated operations separately
• API optimizations

Peformance: Queues

Queue

Queues

• Work with API's
• I/O Operations
• Complex DB requests
• Sending emails
• ...

Performance: Caching

Caching

@TODO write something about how freaking terrible situation is in koa ecosystem

Error Handling

What do I use

• Morgan
• Forever
• Node Domain 😳
• zone.js !

Security

Handpicked

• CSRF koa/csrf
• Password Encryption bcrypt
• Escaping escape-html
• Input valiation validator.js
• Headers helmet
• Audit nsp