They don't give much details, but it sounds like a very superficial need that could be accommodated by Redis, Memcached, AppFabric, and on and on. Kind of surprised that they chose MongaDB as it's far from the fastest competitor.
e.g. If I run a query for NAME LIKE 'BLAH%' it stores that resultset. If I run NAME LIKE 'BLAP%' it stores that resultset. If someone else comes and runs either of them, only a direct match will pull my prior results.
It's okay, but it's no big win or case study.