As quickly as possible, with all the speed that one can muster.

जितनी तेजी से संभव हो, जितनी तेज़ी से कोई कर सकता है।

English Usage: She ran to the store as fast as legs can carry one.

Hindi Usage: वह जितनी तेजी से संभव हो सके, दुकान तक दौड़ी।