What is the Alpenglow upgrade on Solana?
Alpenglow is the name of the major consensus change that’s planned for the Solana blockchain in an effort to help speed up the finalisation of blocks.
Since one of Solana’s raison d’être’s is fast transactions speed, this is a notable upgrade which could see finality reduce from the current ~12.8seconds to between 100–150ms. That’s a reduction of almost 100x!
When we compare this to other blockchains;
- Ethereum has 12second slot times with ~12minute finality
- Bitcoin has ~10 minute block times and ~60minute finality
- Stellar has ~6second block time and instant finality
- Near has 600ms block time and 1.2-second finality
Other blockchains may offer faster blocktimes and finality however it’s often at the tradeoff of centralisation or security — otherwise known as the blockchain trilemma (scalability vs decentralisation vs security; pick 2 and sacrifice the 3rd!)
🛠️What exactly is the upgrade going to do? 🛠️
The proposal, known as SIMD-0326, is an upgrade to the foundational consensus components of the protocol to improve the speed and efficiency of validator communication when reaching agreement about the state of the chain.
Solana’s current consensus model is a combination of Proof-of-History and TowerBFT, and through Alpenglow, this will be replaced with:
- Voter: A new super fast consensus protocol that can finalise and slot in just one or two rounds of voting.
- Rotor: A data layer optimisation that helps reduce bottlenecks and increases the speed of broadcasting so that validators can communicate between themselves faster.
With Votor, validators will also start exchanging their votes offchain. This is a notable shift away from the current model which requires validators to publish their votes onchain — an operational time and cost for them which also bloats the Solana ledger. Votor runs in two concurrent paths where if 80% of the staked weight votes then a block can be finalised in a single round, and if 60% of the stake weight votes then it can be done in 2 rounds. This helps to avoid multiple routine rounds.
Rotor replaced something called the ‘Turbine tree structure’ which is the current way that transaction data (shreds) is disseminated across the network, moving from a single leader to all validators through a multi-hop approach that fans out. Instead Rotor has a one hop broadcast model and this significantly reduces the time to propagate blocks across validators.
⚡What will the impact be for users? ⚡
With transaction finalisation in the realm of 100–150ms this will put Solana on par with the speed you get a Google research and how quickly Visa processes transactions.
However a blockchain’s success isn’t about its TPS, finality times, DAS schemes, or cryptographic algorithm selections, it’s about its use cases! And this could open up new and improved use cases on Solana.
“We don’t need faster finality, we need better use cases” TA 2025
It will allow DEXs on Solana to conduct ‘real time’ trading, opening up the potential for high frequency trading. It will allow SOL transactions to move between borders faster than ever before — coupled with an average transaction fee of $0.0032, that’s a strong use case for being a blockchain of choice for remittance. It could also open up ideas around multi-player games, live auctions and real time data streams.
The increased block speed also means a greater total number of blocks per year, so more capacity on chain (which could further reduce transaction fees which are a measure of supply vs demand) but balanced by more transactions paying fees to validators — who also get a reduction in vote complexity and cost. So this looks to be a winner for users, developers building on Solana and even the validators helping to secure the network.
⏱️When is the upgrade coming? ⏱️
The community voted on this proposal and had an impressive 52% validator stake turnout with ~99.6% voting FOR it. In decentralised governance this is impressive as it can be fractious and often hard to get quorum, especially on large scale changes and protocol upgrades.
It’s now slated to come to testnet in December 2025 and follow to mainnet in Q1 2026. It’s ambitious timelines for such a milestone upgrade of the chain, and blockchain upgrades nearly always run late, however it’s going to be interesting to watch this come to life and be battletested on testnet!
