[greggyb]

Hundreds of millions of records in <=3 seconds is not really a big challenge with a good data model and proper indexing on even a single server.

I work for a BI consultancy and we don't even bat an eye until we hit billions of records in a primary fact table.

Certainly the DB server does need to scale vertically to some extent as you pass through the orders of magnitude > 10M. A good columnstore engine is also worthwhile to consider.