Is There a Data Base Storage Engine?

A data base storage system, or storage engine, that splits data in the following way. Some of the data recites on on a disk, and some of the data lives in memory. We take these segments and we merge them, and then we write them down on disk. And every single key that was overwritten or superseded by likit’s next version is just going to be discarded. This way would we reduce the amount of memory that we're using for pretty much older data,. It can reclaim all the space that we were wasting.