An optimization helper which provides a linear order in which keys should be optimized (cache entries most likely to have common data should be adjacent in the list).
If non-null, this function will only return keys relevant to the given key.
An array of groups, each group is an array of key prefixes.
See Implementation
An optimization helper which provides a linear order in which keys should be optimized (cache entries most likely to have common data should be adjacent in the list).