Not to take away from the substance of the article itself, but is anyone else surprised that they have 2 billion "documents", which presumably means active ads/listings? That seems like an awful lot.
The live data is < 1 TB and is still stored in MySQL.
The "set amount of time" typically hovers around 60 days, though our archiving process has been off for several months while the migration took place. So we have some catching up to do--somewhere in the neighborhood of 150 million postings, last I counted.
Were I to guess based on the video, I would say lack of a Perl client and you'd probably end up having to roll too many of your own solutions on top of it?
The archive does have to be accessed by users though, since users can access listings from many years back.
The entire archive seems to be under 4 TB from what he described in the video (2 billion documents at 2 kilobytes each). They do not retain photos.