May 20
1
Google’s John Mueller said that in some cases, if your site goes down, Google may start to remove URLs from its index within two days. This is on a URL by URL basis, so Google needs to see if the URL is not active and then try a couple more times, and if it is still not coming up, Google can remove it from its index within two days.
See the rest here:
Site Go Down? Google May Start Deindexing URLs In Two Days