What is a Hybrid Database?

A database system that uses both on-disk as well as in-memory data storage is known as a Hybrid Database. These kind of databases are used when a system requires high performance but has limited size that only in-memory database systems can provide. This provides the added benefits of durability and low cost of disk-based database systems. In Hybrid Databases, the system makes use of hard disks for saving and retaining data, yet makes use of the memory for data that is in dynamic use to increase performance. Hybrid database provide multiple benefits that include higher system performance , reduced costs and durability as hard disks are more reliable than RAM.

(source: Wikipedia)