In this article, I am going to explain the difference between the coming soon page and maintenance mode page. When they should be used and why? Does that hurt SEO if you use the wrong page?
Coming soon page is used for new domains when the site is under construction. There will not be any SEO issue, as the new site was never indexed.
Maintenance page is useful when the site has some serious error or some service is down for some reason or in case of some routine maintenance.
When you set a maintenance page, the HTTP status code must be 503. That status code notifies the search engines that the site is temporarily down for some planned maintenance. In addition, it does not hurt the reputation of your site for search engines and Google bot knows when to return to your site.
Never use coming soon page instead of maintenance mode page and maintenance mode page without appropriate HTTP status code.
Hope this helps.