NewKVStore initializes a new boltDB key-value store at the directory path specified, creates the kv-buckets based on the schema, and stores an open connection db object as a property of the Store struct.

NumOfVotes specifies the vote cache size.

VotesCacheSize with 1M validators will be 8MB.

BlockCacheSize specifies 1000 slots worth of blocks cached, which would be approximately 2MB.

Store defines an implementation of the Prysm Database interface using BoltDB as the underlying persistent kv-store for eth2.