To be quick on one's feet; to walk or run quickly.
彼は足が早いので、駅まで歩いてもすぐ着く。
He's quick on his feet, so even walking to the station he arrives quickly.
子どもは足が早くて、いつも公園で走り回っている。
The child is quick on their feet and is always running around the park.
足が早い選手は短距離で有利だ。
A fast runner has an advantage in sprints.
Said of food that spoils easily; having a short shelf life (doesn't keep long).
この魚は足が早いから、仕入れたらすぐ売らないといけない。
This fish spoils quickly, so once it's procured it must be sold right away.
生の果物は足が早いので、冷蔵庫で保存した方がいい。
Fresh fruit doesn't keep long, so it's better to store it in the fridge.
手作りのパンは保存料が入っていないため足が早い。
Homemade bread lacks preservatives and therefore spoils quickly.