Indexing the new version of the site?

Question

Google

Hello.
There is a site on it with about 5000 indexed articles, new ones are successfully indexed. To implement the necessary tasks, it was decided to abandon the cms on which he works and rewrite the site from scratch. The database will be filtered, edited and re-entered into a new project.
Actually:
1) 100% of the articles will become unavailable because the links to them will change completely
2) Half of the articles will be deleted altogether
How to deal with such a situation and roll out a new site correctly?

Answer 1

no need to change links, categorically
redirects can be implemented either in the engine of the new site
or separately, by redirects before the new engine, somewhere on nginx

Answer 2

When we had a slightly similar task, we decided to do the following:
Roll out the old site to the old.sitename.com subdomain with the ability to switch to it and with inscriptions that this is the old version, the new one by the link - deleted materials were left on it.
We made a 301 redirect from old links to new ones - for search engines and who came through the link, so that they would immediately get to the new one and not think about the old version.
Links to deleted materials (using the same 301 redirect) lead to the old version of the site old.sitename with inscriptions that this is an archive model and it would be nice for the client to upgrade.
It was implemented simply - all requests went to index.php, so the simplest script was also written there, which checked - if the link is in the deleted database - redirect to the old version, if there are no deleted and transferred ones in the database, then redirect to the new link. Of course, hemorrhoids were still the same, but everything worked out, the teeth dried up.

Answer 3

At a minimum, you need to put redirects from old pages to new ones, and a 404 error with a good splitting menu.
In general, such an overflow will take your positions (if any), you cut out pages with a certain weight (maybe not even quite bad), a certain age.
In order not to lose positions, you need to keep the old URLs, how to do this is up to you.

Answer 4

If all the same, the old links cannot be left, make a 301 redirect to the new ones
. Where the articles were deleted, make 404 if there are no options to leave them somehow