Solana activates Alpenglow, targeting 150ms transaction finality

Solana activated Alpenglow on its mainnet on Oct. 21, replacing the TowerBFT consensus system it had used since 2020 and targeting transaction finality in about 150 milliseconds. The Solana Foundation’s upgrade page says the change affects how validators agree on blocks; sending transactions and running programs are unchanged.

How does Alpenglow change transaction finality?

Under TowerBFT, validators voted by sending transactions to the chain, and full finality took about 12.8 seconds. With Alpenglow, validators send votes directly to each other and combine them into certificates; a block becomes final after one or two rounds of voting, according to the Foundation.

The roughly 150-millisecond figure is the target for finality, not a guarantee that every transaction will settle in that time. The Foundation says finality is when a transaction can no longer be reversed. It also distinguishes finality from block time, which was reduced separately.

What changes for Solana users and apps?

For users, the Foundation says wallets and apps work as before and no action is needed. Faster finality could let services treat transactions as settled sooner; the Foundation cites near-instant confirmation at a point of sale as one possible use.

Decrypt reported that the handoff replaced TowerBFT at slot 459,653,000. Vote transactions have left blocks, so transaction totals that counted validator votes may fall even if user activity does not, the Foundation says.

Developers whose apps only send transactions and read account data do not need to migrate, according to the Foundation. Those that stream or index block data may need to adjust for changes to block production and finality reporting. The upgrade’s second phase, Rotor, is planned for a later release, but has no schedule yet.

Sources and documents

• Solana Foundation’s upgrade page — solana.com