Data deciding to hang around

In order for us to gain a bit more performance out of our existing setup, we can hold copies of our data away from the primary database and use these in preference wherever possible. There are a number of different strategies we could adopt, from transparent second-level caching layers to external key-value object storage. The detail and exact use of each varies significantly depending on the technology or its place in the architecture, but the main desire of these systems is to sit alongside the primary database infrastructure and attempt to protect it from an excessive load. This would then tend to lead to an increased performance of the primary database by reducing the overall dependency on it. However, this strategy tends to be only particularly valuable as a short-term solution, effectively buying us a little more time before the database once again starts to reach saturation. The other downside is that it only protects our database from read-based load; if our application is predominately write-heavy, this strategy has very little to offer.

So our expanded architecture could look a bit like the following figure: