The total size (denoted in virtual bytes) of all transactions waiting in the mempool.

This is the Point-in-Time (PiT) variant of Mempool Transactions Size. PiT metrics are strictly append-only and their history is immutable. The historic data does not necessarily reflect the best current knowledge, but the information at the time when a data point was first computed. PiT metrics are ideal candidates for applications in model backtesting and related quantitative purposes. Read our article on PiT metrics for more information.