Data deciding to hang around
In order to improve the performance of the existing setup, we can hold copies of our data away from the primary database and use them in preference wherever possible. There are a number of different strategies that we can adopt, from transparent second-level caching layers to external key-value object storage. The details and exact use of each varies significantly, depending on the technology or its place in the architecture, but the main aim of these systems is to sit alongside the primary database infrastructure and attempt to protect it from excessive load. This would then likely lead to an improved 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 its saturation point. The other downside is that it only protects the database from read-based load. If an application is predominately write-heavy, this strategy has very little to offer.
So, the expanded architecture looks like the following figure:
