How to close a product without wrecking the domain

Closing a product usually gets treated as deleting it. It is not. The domain keeps existing, so do the indexed pages and everybody else's links to them, and each of those can be broken separately.

Decide what the old URLs do

Retired pages should return 404 or 410, not redirect to the homepage. A blanket redirect looks tidy and behaves badly: someone following a link to a specific thing lands somewhere that is not it, with no explanation. Search engines treat mass redirects to an unrelated page as soft 404s anyway, so the tidiness buys nothing.

Redirect only where the destination genuinely replaces the source. Otherwise say the page is gone, and give people somewhere useful to go next.

Tell people, and leave it up

Publish a plain explanation and keep it published. People who used the product will look for one, and a domain that quietly turns into something else is worse for everyone than a short note saying what closed and why.

Being specific matters here. "We have made the difficult decision to sunset" tells nobody anything. Saying it did not find an audience and cost more than it returned is shorter and actually informative.

Back up before you are certain

Take the backup before you start, not when you think you need one. The expensive ordering is: delete, discover something mattered, no longer have it.

• Export the data people entrusted to you before touching anything.
• Keep the source. Questions about how something worked outlive the thing itself.
• Verify the backup by reading it back. An archive nobody has opened is a hope, not a backup.

Deleting the code is the easy half. The domain and the links keep living without it.