What Is the Concept of “Finality” in a Blockchain and How Does It Relate to Confirmation Speed?

Finality is the guarantee that once a transaction is confirmed in a block, it cannot be reversed or altered. It is the point at which a user can be absolutely certain their transaction is permanent.

Confirmation speed is the time it takes for a transaction to be included in a block. While a fast confirmation speed is desirable, true finality, especially in Proof-of-Stake, often requires additional time (e.g. two epochs in Ethereum) after confirmation to achieve the irreversible guarantee.