Speed generates quick pressure. Pressure doesn't always require a ton of shifting and pre-snap adjustments. "Kuckus" shows us a simple way to generate pressure that gets results.
Tempo is key. Arrive too late and give up big plays, but getting there fast might shake an opponent's timing for the entire game.
Mix in some plays with a blitzing defensive back. When a corner or a safety rushes, the offensive pass protection scheme has to widen to pick up edge pressure. The resultant gaps are easily exploited in one-on-one match-ups with defensive linemen. When offensive tackles are occupied and backs release, no one is left to block a rushing DB. Some quarterback have speed to get away from defensive linemen and linebackers, but won't be able to run away from a defensive back.
Rushing a defensive back is most effective when teams have a defensive line that can generate pressure with four players and a secondary that can hold up in coverage. Offensive opponents that operate from 3 or 4WR sets, make sure to rush from a nickel, dime, quarter, or dollar formations with enough defensive backs to cover all eligible receivers.
Against the run, rushing defensive backs penetrate the backfield quickly and stress the offense to account for play-side penetration. When the run is opposite the pressure, the blitzing DB will will flatten down the line and stop slow developing runs for a loss or chase down the run from the rear.