$ npm install koa-ratelimit

const Koa = require('koa');
const ratelimit = require('koa-ratelimit');
const Redis = require('ioredis');
const app = new Koa();

// apply rate limit

app.use(ratelimit({
  driver: 'redis',
  db: new Redis(),
  duration: 60000,
  errorMessage: 'Sometimes You Just Have to Slow Down.',
  id: (ctx) => ctx.ip,
  headers: {
    remaining: 'Rate-Limit-Remaining',
    reset: 'Rate-Limit-Reset',
    total: 'Rate-Limit-Total'
  },
  max: 100,
  disableHeader: false,
  whitelist: (ctx) => {
    // some logic that returns a boolean
  },
  blacklist: (ctx) => {
    // some logic that returns a boolean
  }
}));

// response middleware

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

app.listen(3000);
console.log('listening on port 3000');

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

// apply rate limit

const db = new Map();

app.use(ratelimit({
  driver: 'memory',
  db: db,
  duration: 60000,
  errorMessage: 'Sometimes You Just Have to Slow Down.',
  id: (ctx) => ctx.ip,
  headers: {
    remaining: 'Rate-Limit-Remaining',
    reset: 'Rate-Limit-Reset',
    total: 'Rate-Limit-Total'
  },
  max: 100,
  disableHeader: false,
  whitelist: (ctx) => {
    // some logic that returns a boolean
  },
  blacklist: (ctx) => {
    // some logic that returns a boolean
  }
}));

// response middleware

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

app.listen(3000);
console.log('listening on port 3000');