I'm learning about the mempool and found this text on a bitcoin educational site: Once the Mempool reaches full capacity, nodes start prioritizing transactions by setting up a minimal transaction fee threshold. Transactions with a fee-rate lower than the threshold are immediately removed from the Mempool.
If a transaction is removed from the mempool, where does it go? To some holding area, I assume, for possible inclusion in the next block? What is the name of the holding area and where does it reside? Thx.
One of the reasons why a node reject a transaction is because of the lower transaction fee and this may be seen after it has been long due for confirmation but still remains on the mempool because of low transaction fee, we could always avoid this by ensuring to look into the mempool size and fee rate before making a transaction.
To your question in proper, a transaction is sent back to the senders wallet if the node reject it for some particular reason, but i keep wondering why some node may not do the same for overstayed transactions unconfirmed, they remain on the mempool and were not rejected for long.