Sub-Second Finality in Blockchains
Sub-second finality refers to the ability of a blockchain network to confirm and make a transaction irreversible in less than one second
1. This near-instant settlement is considered a critical factor for maintaining a positive user experience, as users expect instantaneous responses similar to those found in traditional web applications
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Importance and Context
The demand for efficient, transparent, and rapid transactional systems is growing as the world becomes more interconnected
1. For applications that require low latency, such as fully on-chain games or certain decentralized applications (DApps), near-instantaneous finality is crucial
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Current Ethereum Virtual Machine (EVM) blockchains often have time-to-finality (TTF) ranges from several seconds to days, which falls short of these expectations
2. While Layer 2 (L2) rollups can achieve high throughput, they typically introduce significant delays in finalizing transactions due to challenge periods, which is problematic for applications requiring near-instant finality
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Blockchains Achieving or Aiming for Sub-Second Finality
Several blockchain projects and mechanisms are designed to achieve or enhance finality speed:
- Avalanche achieves finality in under one second through its underlying consensus mechanism 1.
- Gravity is a Layer 1 blockchain that aims to deliver sub-second finality using a pipelined AptosBFT consensus engine and a parallel EVM runtime (Grevm) 32.
- Solana maintains sub-second finality alongside low transaction costs, even when implementing new features like zero-knowledge (ZK) powered encrypted token standards for institutional compliance 4.
- Sonic is an EVM Layer-1 blockchain that achieves 10,000 transactions per second with sub-second finality, ensuring immediate and irreversible transactions with zero risk of rollbacks 5.
Mechanisms for Fast Finality
Various protocols and mechanisms are being developed to reduce transaction finality times:
- Fast Finality Layers: These are specialized layers designed to significantly reduce transaction times.
- The NEAR Foundation and Eigen Labs partnered to develop a "fast finality layer" for Ethereum Layer 2s, aiming to reduce transaction times from minutes or hours down to 3–4 seconds 6.
- The Astar Network, AltLayer, and EigenLayer collaborated to implement a Fast Finality Layer for the Soneium ecosystem, utilizing AltLayer's MACH for real-time rollup state validation and EigenLayer's restaking mechanism for security 7.
- AltLayer also launched BLITZ, a decentralized fast-finality network for Arbitrum Orbit chains, which uses Bitcoin staking through Babylon for economic collateral to achieve finality 8.
- Subcommitments: Scroll Research introduced subcommitments, a mechanism that provides fast off-chain finality for rollups without requiring immediate on-chain data availability 9. This allows the sequencer to submit succinct cryptographic representations of L2 state transitions more frequently than full data commitments, enabling faster finality for applications requiring shorter confirmation times 9.
- Fast Finality Mechanism (BEP-126): This mechanism, introduced to the Binance Smart Chain (BSC), involves validators signing blocks, aggregating votes, and setting the aggregated vote attestation into the new block's header. A block is considered finalized if two consecutive blocks have been justified, which reduces the chance of chain re-organization 10.