Some years ago, the first PCs had a whopping 256KB of RAM and dual 5.25" floppy drives. No hard drives as they were incredibly expensive at the time. These limitations resulted in having to physically swap floppy disks due to a lack of memory when working with large (for the time) amounts of data. If only there was a way back then to only bring into memory the data I frequently used, as in a subset of the overall data.
Modern applications aren't immune from exhausting resources. MongoDB keeps frequently accessed data, referred to as the [working set](https://docs.mongodb.com/manual/reference/glossary/#term-working-set), in RAM. When the working set of data and indexes grows beyond the physical RAM allotted, performance is reduced as disk accesses starts to occur and data rolls out of RAM.
↧