Google has sophisticated algorithms to determine the optimal crawl speed for a site. Our goal is to crawl as many pages from your site as we can on each visit without overwhelming your server's bandwidth. In some cases, Google's crawling of your site might be causing a critical load on your infrastructure, or cause unwanted costs during an outage. To alleviate this, you may decide to reduce the number of requests made by Googlebot.
If you decide to reduce the Googlebot crawl rate, here are some options:
Reduce crawl rate with Search Console (recommended)
To quickly reduce the crawl rate, you can change the Googlebot crawl rate in Search Console. Changes made to this setting are generally reflected within days. To use this setting, first verify your site ownership. Make sure that you avoid setting the crawl rate to a value that's too low for your site's needs. Learn more about what crawl budget means for Googlebot.
Let Google reduce the crawl rate automatically
If you need to urgently reduce the crawl rate for short period of time (for example, a couple of hours, or 1-2 days), then return an informational error page with a 500, 503, or 429 HTTP result code instead of all content. Googlebot reduces your site's crawling rate when it encounters a significant number of URLs with 500, 503, or 429 HTTP result codes (for example, if you disabled your website). The change is reflected both in the crawling of the URLs that return these errors, as well as the website overall. Once the number of these errors is reduced, the crawl rate will automatically start increasing again.