This April 2025, Solana announced a major upgrade to its core. The network introduced a new consensus protocol called Alpenglow. This is the biggest change to Solana’s design since its creation.
Alpenglow replaces the older components TowerBFT and Proof-of-History (PoH). It adds two new systems: Votor for block voting and finalization, and Rotor for fast communication across the network.
Thanks to these changes, Solana expects to finalize blocks in about 150 milliseconds on average. In some cases, blocks may finalize in just 100 milliseconds. This is faster than any Layer 1 blockchain has done before.
These numbers don’t just mean that Solana is quick. They mean Solana may soon be fast enough to match how real-time Web2 apps like Google or PayPal respond.
A Simpler, Faster Structure With Votor and Rotor
Before Alpenglow, Solana used TowerBFT to finalize blocks. This system worked, but it required many steps and confirmations. That added delay to every transaction. It also used PoH to organize blocks by time, which made the process more complex.
Now, with Alpenglow, Solana has a cleaner and faster setup.
Votor is the new voting engine. It handles block approval and confirmation.
Rotor sends data across the network quickly and directly.
Together, these tools speed up the entire system.
How Finality Speeds Up
Under TowerBFT, a block needed about 12.8 seconds to become final. That’s nearly 13 seconds for every confirmation. To improve this, Solana once used a method called optimistic confirmation. It helped in some cases but wasn’t reliable.
With Alpenglow, the finality is no longer just “optimistic.” It is real and fast.
Votor uses two paths at once:
If 80% of validators vote fast, the block finalizes in one round.
If only 60% vote quickly, it finishes in two rounds.
The network doesn’t wait to choose. It runs both rounds together. Whichever one finishes first confirms the block. This is how Solana now gets to 150 ms or less finality.
Rotor: How Data Moves Around the World
One big reason for this upgrade is how data moves.
In the past, Solana used Turbine, which broke blocks into small parts and sent them out across the network. That system helped speed up things and used everyone’s bandwidth to spread data. Rotor takes the same idea but improves it.
Rotor adds:
A single relay layer instead of many layers;
Fewer steps (or “hops”) between validators;
A better way to choose who relays the data;
Smarter use of network speed and bandwidth.
It also uses the power of each validator based on their stake — meaning bigger participants help more. This avoids overloading any one part of the system and prevents slowdowns.
Rotor works so well that its limits are now based on real-world physics. In some cases, the delay is due to the speed of light, not the software.
Latency Test: Why Zurich Was Chosen
To show how fast Alpenglow can work, the team ran tests with a leader validator in Zurich, Switzerland. Validators from around the world took part. The graph below shows how long it took each validator to reach four steps:
Green bars = network delay
Yellow = time for Rotor to spread the block
Red = when a validator saw notarization from 60% of stake
Blue = full finalization
Some results from this test:
65% of Solana’s stake is within 50 ms of Zurich;
Finalization happened in under 200 ms for most of them;
Only a few nodes far from Zurich had over 200 ms latency.
This proves that network distance — not software — is now the main delay factor.
How Alpenglow Works with Slow or Bad Nodes
The speed in Alpenglow comes from combining many smart ideas:
Running both voting rounds at the same time;
Spreading data quickly with Rotor;
Using validator bandwidth better;
Reducing how far data needs to travel;
Picking relayers carefully;
Supporting voting even if up to 40% of stake is slow or not honest.
Alpenglow uses a “20 + 20” rule. It can keep working even if 20% of validators try to cheat and another 20% don’t answer at all.
It also uses low-variance sampling — a way to choose validators that avoids bias and keeps block processing stable.
Why This Change Is Important
Solana already had high speed in how many transactions it could process. But it still took a few seconds to say that a block was final. That’s not enough for things like:
Real-time games;
Fast trading platforms;
Web2-like user interfaces;
Stablecoins that need instant confirmation.
Alpenglow brings Solana into a new category. It’s not just fast in throughput, but fast in response time.
That means users can now click and see results as quickly as they would on PayPal or Stripe — but on a fully decentralized system.
What Was Removed — And Why
To reach this level of speed, Solana had to say goodbye to TowerBFT and PoH. These were strong systems. They helped Solana grow early on.
But both had limits:
TowerBFT needed several rounds of voting;
PoH depended on timing and exact schedules.
Alpenglow removes these steps. Instead, it uses direct messaging, parallel voting, and a simple but strong data layer. The result is fewer delays and more flexibility.
Scientific Backing and White Paper
Alpenglow is not just theory. It’s built on real research. The Solana team created a white paper to explain how it works.
This document includes:
Clear definitions;
Simple explanations;
Example code (pseudocode);
Graphs and simulation tests;
Formal proofs of correctness.
The team didn’t just guess. They tested everything using Solana’s current mainnet stake distribution. The results show that the system is both fast and secure.
What Alpenglow Changes for Solana’s Future
Alpenglow brings a new way for Solana to handle apps that need very fast response times. With this system, the network can finish blocks in just 100 to 150 milliseconds. That’s faster than many systems that are not even decentralized. This speed doesn’t just make things quicker — it creates new ways to use the blockchain.
The upgrade replaces older systems like TowerBFT and PoH. In their place, it uses tools called Votor and Rotor. These tools help move data faster and use the network’s power more wisely. Because of this, Solana is now better prepared to support apps that need to react right away — like games, payment apps, or trading platforms.
If more developers start using Alpenglow, it could help Solana grow into new areas. These are areas where being fast and steady is very important. This wouldn’t just speed up today’s apps. It might also lead to new kinds of tools — ones that expect a blockchain to answer as quickly as a cloud service.
Solana would then stop just following what users ask for. Instead, it could lead the way and show what’s possible. That’s a big change — from being one of the fast blockchains to becoming the one that sets the pace for what blockchains should do next.
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