Solana transactions still take over 12 seconds to reach finality — far too slow for real-time trading and gaming. The upcoming Solana Alpenglow upgrade promises to cut that to just 150 milliseconds. Can it really deliver, and what does it change under the hood? Let’s see. Solana (SOL) has long been seen as a fast blockchain. Its design, built around Proof of History (PoH) and Tower BFT, allows it to process thousands of transactions per second. PoH acts as a cryptographic clock that orders events, while Tower BFT coordinates validator votes to reach agreement on blocks.