Currently , lbrycrdd loads the entire claimtrie composed of CClaimTrieNode's into memory
The total size of CClaimTrieNode's can exceed what is available in memory so we need to create a cache that will keep a fixed size of CClaimTrieNode's as needed, and store the rest on disk.

Say we create a class CClaimTrieCache, perhaps something like this in pseudo-code (just trying to brainstorm here, open to different approaches).

CClaimTrieCache(int num_nodes_in_cache) : num_nodes_in_cache is the max number of CClaimTrieNode that can be loaded into cache

public methods:

void loadFromDisk() : loads as much CClaimTrieNode's as possible, runs on startup

*CClaimTrieNode root(): This always returns a pointer to the root claim trie node

nodeMapType::iterator children(CClaimTrieNode *node) : Returns an iterator for CClaimTrieNode.children that allows for the traversal of the claimtrie. If the children nodes of "node" has not been loaded into cache, than this means that CClaimTrieCache will need to load it from disk into cache.

Note that currently CClaimTrieNode's are stored on disk using key value storage where the key is the node name. The "children" of CClaimTrieNode's are not stored on disk, they are loaded when they are put into memory ( see InsertFromDisk() https://github.com/lbryio/lbrycrd/blob/master/src/claimtrie.cpp#L1108 ).

Thus this means that for the disk storage of CClaimTrieNode we should store a vector of children letters on disk as well. This will allow us to look up all of the node's children efficiently in the key value storage.

I think for the cache to have efficient performance, we need to eject based on the depth of the node and maybe distance from the new node being inserted? The logic is that if a CClaimTrieNode is closer to the root, it will see far more accesses to it rather than if it further from the root.