I see eosflare.io can list accounts that has transactions/actions with a specific smart contract. How?
For example, here is eosflare.io's list of all DICE token holders: https://eosflare.io/token/betdicetoken/DICE
Here is the list of RIDL token holders: https://eosflare.io/token/ridlridlcoin/RIDL
They even have them ranked! Is this possible via RPC API or they are doing it by storing all the actions in a database and then producing a nice report from it?