What is the best solution when you know the approximate time of maintenance work on your website?

The 503 Service Unavailable status code indicates that the server is temporarily unable to handle the request due to temporary overloading or maintenance of the server. When combined with the Retry-After header, it explicitly tells search engine crawlers (and browsers) how long they should wait before attempting to re-crawl the page. This prevents crawlers from indexing an incomplete or broken version of your site and ensures they return once maintenance is complete, preserving your SEO. Using a 500 status code is too general and doesn't provide the retry instruction. A 200 status code indicates success, which is misleading during maintenance. A noindex directive in robots.txt would prevent indexing permanently, which is not the goal for temporary maintenance.