What would you do for a small site, and what would you do differently for a larger site who sees this type of thing often?
Would you 301 redirect? If so, where?
Would you turn it into customized 404 Error page with a link to somewhere else on the site?
Would you do anything differently for a site over 100k pages vs a site with 10k pages?
How would you deal with product pages that will no longer be used?
Any product that no longer will be restocked should be redirected to the parent category of the brand if your site has each product by brand collections or to the category of relevant products. And I would do the same thing for a site that's 10 products and 10k... a soft 404 is taxing to Google as is 404 and reduces the crawl budget
It depends, are those pages currently bringing in organic traffic to your store? If yes what's the volume of the traffic, what products specifically? Are there alternatives to these products that you can link to from this page?
I always refer to Amazon when it comes to this question.
- Product out of stock but coming back -> Leave the page as HTTP 200, reference similar products, and announce when you expect the product to be back in stock
- Product out of stock but not coming back -> redirect the page to the category or brand page