The UTXO set is stored on the disk, but some UTXOs are also stored in the cache. When validating a transaction, you need to query the UTXO pointed to by the input of the transaction. First, you go to the cache to find it, if it’s not found, you need to go to the disk to find the UTXO. Due to the characteristics of levelDB, the UTXO searched on the disk needs to be written into the cache. If the cache is full at this time, how does the node make room in the cache for the UTXO just found?