I have a question about multi-vendor e-commerce portal.
Sellers offer particular offer for a time-being. For each offers, a new webpages are created, they are listed in site-map and crawled by Google.
My client doesn't want to show those pages once the offer is expired. So how to setup an auto-expiration of those web-pages? I am looking for the methods for asp.net technology. Can I achieve it using HTTP header, or do I need to do something with database and server query?
Once those pages are expired, then should I remove from sitemap? How does that affect in Google's indexation? Are those pages show up under 404 errors in Google Search Console? If yes, then after a few months, there will be a long list under 404 errors.