Why does eBay use different databases for listing vs. buying?

[revenue-collector]

I go to list a music CD and start by scanning the UPC do prefill as much as possible... product not found. But then on a whim I do a search on eBay as a buyer for the same UPC code and it pulls up the correct items!

Why the [CENSORED] is eBay using DIFFERENT databases/lookups on the back end from what is used on the front end?

This is so monumentally stupid. Just when I think that eBay can't screw things up worse, they surprise me... and not in a good way.

[shipscript]

Why does eBay use different databases for listing vs. buying?

Because the data in those databases are quite different.

The database that you would access on the listing creation form is typically supplied by a third party data supplier, like Bowker Books for ISBNs. The catalog data automatically fills in the Item Specifics. If that third party supplier does not have the UPC that you entered, then it won't populate.  This is a GTIN-centric database (UPC/EIN/ISBN).

The search is an entirely different animal. eBay indexes listings (right after they are posted) to extract the keywords to use in response to a buyer search. Listings that have a UPC in the Item specifics will be found if a UPC is entered in search. This search will look for words indexed from Item Specifics, title, description, and category name.

However, eBay also has a taxonomic search that can be seen when starting from the home page and working through the categories shown at the top of the home page.  That search works a little differently than a keyword search as it looks at eBay's own catalog to find best matches in a catalog search, and will pull in other listings that match that catalog item. Catalog items will typically have a product rating, or the ability to rate the product.

[revenue-collector]

One would think that eBaycould correlate one to the other. In other words, if a upc lookup in the listing db provides zero hits, do a second query against the search db to see whether any alternative hits exist. There are ways to get there from here.

If I can do a upc search in listings, find a result, click the "got one to sell?" (or whatever the link is) and have the information prefilled from that listing, then eBay certainly could do something similar under the hood, especially given their resources.