In distributed systems, "Finality" refers to the guarantee that a transaction cannot be reversed. Near Protocol uses a specialized consensus gadget called Doomslug to achieve this faster than traditional BFT (Byzantine Fault Tolerance) models.
The Problem with Traditional BFT
In older networks (like Cosmos or early Polkadot models), reaching consensus often required two or more rounds of communication between nodes.
- Round 1: "I propose this block."
- Round 2: "I agree with this block."
- Round 3: "I confirm we all agreed."
This "chatter" creates network latency.
How Doomslug is Different
Doomslug allows the network to achieve "Practical Finality" after just one round of communication.
- The Proposal: A block producer creates a block.
- The Endorsement: Other nodes send an endorsement.
- Result: Once the block has more than 50% of endorsements, it is considered "Doomslug Final."
Technically, it is irreversible unless at least one validator is slashed (penalized) for malicious behavior.
The "Finality Gadget"
While Doomslug provides instant practical finality (allowing dApps to feel fast), a separate background process runs to provide full BFT security. This ensures that even if the network partitions (splits in half), the chain can eventually recover and reconcile the true history without manual intervention.
For developers, this means Near offers the best of both worlds: the speed of a single-round consensus with the heavy security of a multi-round BFT backing it up.