How to implement the removal of a product withdrawn from sale in the aggregator?

Question

Parsing

I am making a commodity aggregator, for about 100k-200k goods. The problem is that the availability of goods remains relevant, i.e. the parser collects data, gives me csv, I compare it with the original database, select the changed data and load the changes into the database. But what if the item was taken off the market? The parser will not collect data about it, no changes will be loaded, it will hang like a dead weight.
The only option that I see so far is a complete database update after each data collection, but this is an impossible load on the server. Ideas?

Answer 1

write down the update time, if N hours have passed after it, do not show this product.