Also, am I right to say that the introduction of this new feature means that unlike other cryptocurrencies I would be able to pay for coffee and not to wait until my transaction is completed?
No, it just tells you if a tx with an output belonging to you is in the mempool or not. Previously you had to wait about 2 minutes for it to enter a block to see if it was there or not. It's not instant tx, it's more like "did any of the transactions I saw recently on the network have funds belonging to me". I think it was a Bitcoin core wallet feature from day one.
Nice answer! Thank you!
