Solana activates Alpenglow, targeting 150-millisecond finality

Solana activated its Alpenglow consensus upgrade on Wednesday, Oct. 21, replacing TowerBFT with a system designed to cut transaction finality from 12.8 seconds to about 150 milliseconds, according to the Solana Foundation’s Alpenglow upgrade record.

How does Alpenglow change transaction finality?

Alpenglow lets validators send votes directly to one another and combine them into certificates, instead of recording votes as on-chain transactions. The change allows a block to become final after one or two voting rounds, the Foundation says.

Under TowerBFT, validators recorded votes on-chain and approvals accumulated over 32 slots. The 150-millisecond figure is Alpenglow’s target for finality, when an application can treat a transaction as settled; it is not the time between blocks.

When did the new consensus take over?

The Foundation says Alpenglow activated at the start of epoch 1064, at about 13:36 UTC on Oct. 21. TowerBFT continued for a 5,000-slot transition window; the new consensus took over at slot 459,653,000.

The Foundation records that 446 of 654 participating validators certified the preceding block, and that the handover took about 900 milliseconds. The Block also reported the activation, citing a statement from Solana engineering firm Anza, which said the upgrade retires TowerBFT, in use since Solana launched in March 2020.

What changes for users and developers?

Wallets, apps, transaction formats and fees remain unchanged, according to the Foundation. Vote transactions no longer appear in blocks, so dashboards that counted them may report lower transaction totals after activation.

Alpenglow’s rollout also includes Rotor, a planned change to how block data spreads across the network. The Foundation says Rotor is not yet scheduled.

Sources and documents

• Alpenglow upgrade record — solana.com