Get past request limit in crawling a web site

OK, first and foremost: if a website doesn't want you to crawl it too often then you shouldn't! It's basic politeness and you should always try to adhere to it.

However, I do understand that there are some websites, like Google, who make their money by crawling your website all day long and when you try to crawl Google, then they block you.

Solution 1: Proxy Servers

In any case, the alternative to getting a bunch of EC2 machines is to get proxy servers. Proxy servers are MUCH cheaper than EC2, case and point: http://5socks.net/en_proxy_socks_tarifs.htm

Of course, proxy servers are not as fast as EC2 (bandwidth wise), but you should be able to strike a balance where you're getting similar or higher throughput than your 50 EC2 instances for substantially less than what you're paying now. This involves you searching for affordable proxies and finding ones that will give you similar results. A thing to note here is that just like you, there may be other people using the proxy service to crawl the website you're crawling and they may not be as smart about how they crawl it, so the whole proxy service can get blocked due to the activity of some other client of the proxy service (I've personally seen it).

Solution 2: You-Da-Proxy!

This is a little crazy and I haven't done the math behind this, but you could start a proxy service yourself and sell proxy services to others. You can't use all of your EC2 machine's bandwidth anyway, so the best way for you to cut cost is to do what Amazon does: sub-lease the hardware.

Using proxies is, by far, the most common way to tackle this problem. There are other higher-level solutions that provide a sort of "page downloading as a service" guaranteeing you get "clean" pages (not 404s, etc). One of these is called Crawlera (provided by my company) but there may be others.

For this case I usually use https://gimmeproxy.com which checks proxy every second.

To get working proxy, you need just to make the following request:

https://gimmeproxy.com/api/getProxy

You will get JSON response with all proxy data which you can use later as needed:

{
  "supportsHttps": true,
  "protocol": "socks5",
  "ip": "156.182.122.82:31915",
  "port": "31915",
  "get": true,
  "post": true,
  "cookies": true,
  "referer": true,
  "user-agent": true,
  "anonymityLevel": 1,
  "websites": {
    "example": true,
    "google": false,
    "amazon": true
  },
  "country": "BR",
  "tsChecked": 1517952910,
  "curl": "socks5://156.182.122.82:31915",
  "ipPort": "156.182.122.82:31915",
  "type": "socks5",
  "speed": 37.78,
  "otherProtocols": {}
}