Solana activates Alpenglow consensus, targeting 150ms finality

Solana activated Alpenglow on mainnet on October 21, replacing TowerBFT’s consensus process with Votor, a validator voting protocol designed to finalize blocks in one or two rounds. The Solana Foundation’s Alpenglow documentation says the switch began at epoch 1064, targeting finality in roughly 150 milliseconds, compared with about 12.8 seconds under TowerBFT. That is a target for final settlement, not a promise that every transaction will appear on every user’s screen in that time.

The change affects how validators agree on blocks. It does not change how Solana executes transactions. The SVM, transaction formats and fee mechanics remain the same, so users can continue to send transactions with their existing wallets and apps.

How does Alpenglow finalize blocks faster?

TowerBFT recorded validator votes as transactions and built up approvals over successive slots. Under Votor, validators send votes directly to one another and bundle them into certificates. A block can then become final after one or two voting rounds, without vote transactions occupying block space.

The handover used a certified genesis block. The Foundation says 446 of the network’s 654 validators voted to certify the block at slot 459,652,999; Alpenglow consensus took over at slot 459,653,000. CoinDesk also reported that the transition itself took about 900 milliseconds. That timing describes the migration between consensus systems, not the new target for transaction finality.

Alpenglow changes consensus, the process for agreeing on transaction order and finality. It does not make blocks arrive every 150 milliseconds. Solana’s slot time was reduced separately, from 400 milliseconds to 200 milliseconds, in a change completed in October.

What changes for a payment or deposit?

Finality tells an app when it can treat a transaction as settled and no longer reversible. Faster finality can let a merchant release goods or an exchange credit a deposit sooner, with less waiting for the network’s final settlement signal. CoinDesk reported that how soon users see that signal also depends on the service relaying it; some systems may receive finality information later than validators participating directly.

The 150-millisecond figure is a target under normal network conditions, not a guarantee for each payment. Apps may already show a transaction as confirmed before it reaches finality, so the user-visible difference depends on how each service handles confirmation and settlement. Solana’s documentation says `confirmed` and `finalized` now describe the same state, while `confirmed` is slated for removal in a later release.

Why could Solana’s transaction count fall?

Vote transactions no longer appear in blocks. Dashboards that counted validator votes as transactions may therefore report lower totals after activation, even if user payments and trades have not fallen. Historical comparisons need to account for that change in what gets counted.

For people who only send transactions or use onchain programs, no migration is required. Developers who stream or index block data face different requirements: Geyser events now carry a `bank_id`, and indexers must handle that field rather than assume one block per slot. Those are data-consumption changes around consensus; they do not alter the transaction a user signs or the fee paid to send it.

Sources and documents

• Solana Foundation’s Alpenglow documentation — solana.com