Although I agree with eleman here, whenever an application requires to a (full-fledged) database to operate, it is a serious consideration to store the results of queries etc. into RAM. Using more RAM for the application means it will be much more responsive, because retrieving and storing in a database is "expensive". Not only time-wise (responsiveness), but you also introduce an extra factor for reliability, especially when you need to access databases off-site.
Nowadays computers have quite a lot of RAM onboard and usually decent connections to (off-site) databases. However, you cannot trust to have a decent connection 100% of the time, while the RAM is a much more stable resource. For a good (newbie) user-experience, the trend is to use the most stable resources at hand.