What is the Waste Metric?
Coin Selection Funds are tracked in discrete portions, so called Unspent Transaction Outputs (see UTXO model). Generally, a wallet’s funds are split across multiple to numerous such UTXOs. When a user sends a transaction, their wallet software needs to pick some of their UTXOs to fund the transaction. The process of picking the input set of a transaction is referred to as Coin Selection. The primary goal of Coin Selection is to raise sufficient funds to pay for the recipient outputs and fees of the transaction, but there are secondary goals as well: