Solana switches to Alpenglow, targeting 150ms finality

150 milliseconds is the finality target for Alpenglow, which Anza activated on Solana mainnet on October 21. That is the point when a transaction can no longer be reversed, letting apps treat a payment or trade as settled.

Solana’s Alpenglow upgrade page says the protocol went live at epoch 1064, replacing TowerBFT, the network’s previous consensus system. Anza told The Block that the change targets a drop from about 12.8 seconds to 150 milliseconds.

What changes in the way Solana reaches finality?

Alpenglow replaces on-chain validator vote transactions with direct messages between validators. They bundle votes into certificates, which confirm that enough stake backs a block.

Under the old TowerBFT system, validators cast votes as transactions, and enough votes accumulated across 32 slots for a block to become final. With Alpenglow’s Votor protocol, a block can become final after one or two rounds of voting, according to Solana’s upgrade documentation.

The handoff took place at slot 459,653,000, after the network began epoch 1064 on October 21. Solana’s page says the genesis block was certified with votes from 446 of 654 validators.

Does 150 milliseconds mean every transaction settles that fast?

No. Solana and Anza describe 150 milliseconds as a target, not a guaranteed time for every transaction. The actual wait can vary with network conditions and with how quickly an app or service receives finality information.

Finality also differs from block time. Solana says block time was separately reduced from 400 milliseconds to 200 milliseconds in four stages completed in October. Alpenglow’s 150-millisecond figure describes how quickly a transaction becomes irreversible, not how often the network produces blocks.

What will users and developers notice?

For users, wallets and apps continue to work as before, and transaction fees and execution are unchanged. Faster finality could help an exchange credit deposits sooner or a merchant confirm a payment with less waiting, though the target does not guarantee each service will display the update at that speed.

Developers and data providers will see a change in block contents: validator votes no longer appear as transactions. That can lower reported transaction totals, so comparisons with earlier activity need to account for the votes that used to be counted.

Alpenglow is rolling out in two phases. Votor, the voting and finality protocol, is live. Rotor, a planned replacement for Solana’s block data distribution system, is still for a later release and has no scheduled date, according to the Solana Foundation.

Sources

• Alpenglow upgrade page — solana.com
• The Block — theblock.co