Solana Targets Sub-Second Finality with Alpenglow Upgrade

Solana is upgrading its consensus protocol in an effort to achieve sub-second finality. The upgrade, called Alpenglow, will replace Tower BFT and Proof of History protocols with two new components: Votor and Rotor.

Votor will introduce a lightweight vote aggregation model that allows validators to aggregate votes off-chain before committing finality. This is expected to reduce theoretical finality from 12.8 seconds to 100-150 milliseconds. Fast Finalization will trigger when a proposed block gains 80% or more of total stake approval in the first round, while Slow Finalization activates when the first round reaches 60% to 80%, requiring a second round exceeding 60% before finalization.

The other upgrade, Rotor, will redesign the block propagation layer and introduce stake-weighted relay paths that prioritize bandwidth-efficient propagation. This is expected to reduce block propagation time from several seconds to as low as 18 milliseconds under typical bandwidth conditions in simulations.

Solana's on-chain trading volume reached $1.6 trillion in 2025, surpassing all exchanges except Binance. The upgrade addresses stability, validator performance, and scalability concerns that have drawn criticism despite the network's speed and low fees.