What is Mempool?

The mempool is the waiting area each node on a blockchain keeps for transactions that have been broadcast but not yet included in a block. A deposit sitting in the mempool has left your wallet and has not arrived anywhere. Miners or validators pick from that pool by fee, so a transaction paying below the going rate can sit there for hours while later, better-paying transactions confirm ahead of it. When the network is quiet the wait is seconds; when it is congested the fee you attached at send time is what decides your place in the queue. This is the single most common cause of a crypto casino deposit that appears to be missing. The site cannot credit an unconfirmed transaction, and support cannot speed it up, because neither party controls the ordering. A block explorer will show the transaction as pending with its fee, which is the evidence to check before opening a ticket. Some wallets can bump the fee on a stuck transaction; if yours cannot, waiting is the only option.