Redirection 302 during DNS update

Question

I will migrate my website from server A to server B.

During the DNS propagation, the users arriving on server A will be 302 redirected (rewrite rule in Apache) to a temporary alias on server B.

Example: A (http://www.mywebsite.com) -> B (http://mywebsite.com.myhoster.com)

When their DNS is updated, they will go to server B (www.mywebsite.com).

After a few days, we will stop server A and remove the alias on server B.

Is it a good practice (SEO and technically)? Or do you have an other idee?

Note: The TTL of the DNS record has been set to 300 to speed the DNS switch.

Answer 1

Redirecting to a temporary alias is a bad idea. What if a new visitor bookmarks it and then the temporary alias is deleted? What if Google visits just then and adds the temporary alias to their search index? TTL of 300 is 5 minutes. It's better to not redirect at all. Just wait the 5 minutes for the DNS to change.