The Alpenglow upgrade targets a reduction in Solana's transaction finality time from approximately 12.8 seconds to roughly 150 milliseconds.

From the articleSolana's Alpenglow test migration success sets stage for mainnet activationAlso in Solana's Alpenglow Upgrade Arrives Oct. 21 With a Major Speed Boost, Solana sets October 21 for massive Alpenglow upgrade that could make transactions 99% faster to finalize