A cryptocurrency node’s method of storing data on pending transactions is called a mempool (a contraction of memory and pool). It serves as a kind of holding area for transactions that haven’t been included in a block yet.
There isn’t a single pool used by every node. Each one has a unique configuration and gets transactions at various times. Higher-end devices could allocate a significant amount of RAM to recording transactions, but lower-end ones with fewer resources might just dedicate a tiny amount.