Mark Millar and Grant Morrison's Flash (Wallace Rudolph "Wally" West of New Earth) disabled Mirror Master's Mirror Gun in one pico-second.
The Flash v2 # 133 (January, 1998) https://dc.fandom.com/wiki/The_Flash_Vol_2_133
Five years later, Joe Kelly's Flash ("Wally") has no time to disable weapons, and risked lifes of children to plow bullets out of the air because arrorganz to snub Superman »Schwachmat«!
Brad Meltzer's official moderate mid-tier DC canon Post-Crisis Superman (Kal-El of New Earth) »Schwachmat« can perceive events that occur for at least a femto-second ...
Justice League of America v2 # 10 (August, 2007) https://dc.fandom.com/wiki/Justice_League_of_America_Vol_2_10
... and Jeckie (Sensor Girl) proves 16 frames (3 pages) later, including spoken sentence, that a female of Orando is faster than a femto-second as a masculine of Krypton on Earth!
Justice League of America v2 # 10 (August, 2007) https://dc.fandom.com/wiki/Justice_League_of_America_Vol_2_10
"Atto-Second"
J. Michael Straczynski's Flash's (Barry Allen of New Earth) speed is so immeasurable that he has moved and reacted by the attosecond.