When should I consider using a in memory database and what are the issue to look out for?

Question

I was just think that now it is common to have enough RAM on your database server to cache your complete database why are the specialist in memory database (e

Answer 1

The trend seems to be to cache aggressively and use the database to populate the cache. Regardless of where the database lives, joins are still expensive so the preference seems to be to do the join once and cache the result in something like Memcached or Velocity.

There are still in-memory databases around and they are used, but it depends upon the context you want to use them. SQLite for example is often used as an in-memory database when testing data layers.