Currently, when having the status change with a transaction in the mempool, bitcoin core will expose informations of the transaction via ZeroMQ. https://github.com/bitcoin/bitcoin/blob/master/src/zmq/zmqnotificationinterface.cpp#L160-L195 Having 3 impact types of the transaction with mempool:
- added.
- blockConnected.
- blockDisconnected.
Informations about impact type is very important with the client that subscribes Zmq channels. In some case, we only care about the new transactions that be accepted to mempool.