Dealing with old records in Scrapy?
How are you storing the data after each run?
You might consider just checking the for existence of a buy button on subsequent scrapings and marking a flag on the item as unavailable.
I'm scrapping data from a subsection of Amazon. I want to be able to detect when a product is no longer available if I have previously scrapped that product. Is there a way to deal with outdated data like this? 
The only solution I can think of so far is to completely purge the data and start the scrapping over but this will cause the metadata assigned to these items to be lost. My only other solution I can think of is an ad-hoc comparison of the two scrappings.