Solana activates Alpenglow, targeting 150ms finality

Anza activated its Alpenglow consensus upgrade on Solana’s mainnet on Oct. 21, replacing TowerBFT and targeting transaction finality in about 150 milliseconds. Finality is the point when a transaction can no longer be reversed. Anza’s announcement says the change is intended to make settlement faster for services such as exchanges crediting deposits and merchants accepting payments.

• Activation: epoch 1064, beginning at about 13:36 UTC on Oct. 21.
• Alpenglow’s target: roughly 150 milliseconds to finality.
• TowerBFT’s stated baseline: about 12.8 seconds.

What changed when Alpenglow went live?

The upgrade replaced TowerBFT, Solana’s consensus protocol since the network launched in March 2020. The Solana Foundation says Alpenglow began consensus at slot 459,653,000; the preceding genesis block was certified by 446 of the network’s 654 validators.

Alpenglow changes how validators agree on blocks. Under the old system, validators recorded votes as on-chain transactions, and enough votes had to accumulate before a block became final. Now they send votes directly to one another and combine them into certificates, allowing finality after one or two rounds of voting, according to the Solana Foundation’s upgrade guide.

Does 150 milliseconds mean every transaction is final that fast?

No. The 150-millisecond figure is a target, not a guaranteed time for every transaction. It describes the time to finality, not how often Solana produces blocks. The Foundation says the target is roughly 150 milliseconds, while actual timing depends on network conditions.

The Block reported Anza’s claim that finality falls from about 12.8 seconds to 150 milliseconds. That comparison uses the previous system’s stated baseline; it does not establish that every transaction on the live network now reaches finality in exactly 150 milliseconds. The difference matters for users and services that need to know when funds are settled, rather than merely shown as confirmed.

What will users and developers notice?

People sending transactions can continue using their existing wallets and apps. The Foundation says transaction execution, programs and fees are unchanged. If the target holds, apps that rely on final settlement, including payment services and exchanges, may be able to act on a transaction sooner.

Some network data will look different. Validator votes no longer appear as transactions in blocks, so dashboards that counted those votes may report lower transaction totals even if user activity has not fallen. The Foundation advises developers who read block streams to account for a new bank_id field and for the possibility that a slot can contain more than one candidate block.

Alpenglow’s launch covers its voting protocol, Votor. A second planned phase, Rotor, is intended to change how block data spreads across the network, but the Foundation says it is not yet scheduled. For now, the confirmed change is the replacement of TowerBFT and the new consensus process; the 150-millisecond figure remains the target to watch as the live network runs.

Sources and documents

• announcement — prnewswire.com
• Solana Foundation’s upgrade guide — solana.com