Is it possible to minimize the negative impact of long site downtime on rankings and SEO? This question was answered by Google employee John Mueller during a webmaster hangout.
According to Mueller, if a site is unavailable for more than a few days, then Google begins to de-index its pages. It is impossible to minimize the consequences of such a long downtime.
If the site is unavailable for about a day, then using the server response code 503 is a great option. However, after a couple of days, Google starts to regard this code as permanent and starts removing pages from the index, says SEOnews.
NIX Solutions notes that once the pages are available again, Google will try to crawl them again. At the same time, they may not immediately return to the search results, and when this finally happens, strong fluctuations in the ranking are possible until the situation returns to normal.
Therefore, if the site is disconnected for more than 2 days, you should expect at least temporary fluctuations in the ranking and take into account that it will take some time to return to the previous levels.
Mueller advises avoiding long site shutdowns if possible.