• Solana has scheduled its Alpenglow upgrade for Oct. 21, targeting transaction finality in about 150 milliseconds, though actual performance will depend on network conditions.
• Alpenglow will replace TowerBFT and move validator votes off-chain, which could sharply reduce Solana’s reported transaction count without reflecting a decline in user activity.
• Validators must use Agave 4.3.0 for the migration, while Firedancer and Frankendancer operators will need to switch software temporarily.

Solana has scheduled Oct. 21 for Alpenglow, a major upgrade aimed at making transactions irreversible in roughly 150 milliseconds by changing how the computers running the network agree on payments.

The updated timetable published by the Solana Foundation sets a date for replacing TowerBFT, the voting system Solana has used since its launch in 2020. The 150-millisecond figure remains a target, with actual performance depending on network conditions.

A Solana payment can already appear successful almost immediately. But Alpenglow aims to give it the stronger guarantee that it cannot be undone almost as quickly.

A merchant waiting for that assurance before accepting a payment, or a bridge before releasing funds on another blockchain, could act sooner.

As of today, validators, or the computers that check transactions and help secure Solana, submit their votes as transactions recorded on the blockchain. Alpenglow will allow them to exchange votes directly and combine enough approvals into a type of certificate that makes a block final after one or two voting rounds.

That could produce an odd result on activation day, however. Solana’s transaction count may fall sharply because validator votes disappear from blocks, even if people keep trading and making payments at the previous pace.

Read More: Solana’s 150-millisecond settlement upgrade reaches second public test network

Validators must also prepare for the switch. Operators need software built on Agave 4.3.0. Firedancer and Frankendancer, alternative programs used to run validators, will not support the initial migration, requiring their operators to switch temporarily.

Removing vote transactions changes what validators pay, too. Their current voting charges of roughly 1 SOL per epoch will disappear, replaced by a flat admission fee of 0.8 SOL. An epoch is a period during which Solana assigns validators their network responsibilities.

The migration is scheduled for epoch 1064, expected to begin around 15:00 UTC on Oct. 21. Solana will continue using its old voting system for the first 5,000 slots, the short windows assigned for block production, before switching to Alpenglow roughly 18 minutes later.