Solana activates Alpenglow, targeting 150-millisecond finality

Solana activated Anza’s Alpenglow consensus upgrade on mainnet on Wednesday, October 21, replacing the system validators have used since 2020 and targeting much faster transaction finality. Anza told The Block that Alpenglow took over at slot 459,653,000 at about 14:00 UTC. The change is designed to cut the time before a transaction can no longer be reversed from about 12.8 seconds to roughly 150 milliseconds.

What changed when Alpenglow went live?

Alpenglow replaced TowerBFT, Solana’s previous consensus protocol. Consensus is how validators agree on the order of transactions and which blocks are final. Under TowerBFT, validators voted by sending transactions, and blocks became final after votes accumulated over multiple slots. The Solana Foundation’s upgrade guide says validators now send votes directly to one another and combine them into certificates, which can finalize a block in one or two rounds.

That change removes vote transactions from blocks. It also changes the meaning of “confirmed” and “finalized”: the Foundation says both now describe the same state under Alpenglow. Transaction execution, programs and fees remain unchanged, according to its guide.

Does 150 milliseconds describe measured performance?

The 150-millisecond figure is a target, not a guaranteed time for every transaction. The Foundation says actual finality depends on conditions including the distribution of stake among validators, and can be faster when a block finalizes in one round. Anza and Solana describe the upgrade as reducing finality from about 12.8 seconds to roughly 150 milliseconds.

Finality matters to exchanges deciding when to credit deposits and merchants deciding when a payment is settled. A shorter wait could make those services feel more immediate, though the target alone does not establish how quickly every transaction will finalize in practice.

What comes next for Solana’s upgrade?

Alpenglow’s first phase, called Votor, handles validator voting and is now live. A later phase called Rotor is intended to change how block data spreads across the network, replacing the current Turbine system. The Foundation says Rotor is planned for a later release but has no schedule yet.

Most users do not need to take action, the Foundation says: wallets and apps continue to work as before. Developers and infrastructure providers that read block data may need to account for changes such as multiple candidate blocks in a slot. The activation changes how Solana reaches agreement; its effect on real-world settlement depends on the network’s performance after the switch.

References

• The Block — theblock.co
• Solana Foundation’s upgrade guide — solana.com