The classic short story has a beginning, middle and end. So does the flash fiction story. It’s just that the beginning of a flash fiction story is as short as possible; the middle is the largest part of the story and the ending is the payoff. How do you know what the payoff is?
The payoff will be one of these three basic endings: summation, change in direction or an epiphany.
A summation ties all the lose ends together with a statement or action that throws the rest of the story into relief.
A change in direction takes the story into a new, unexpected trajectory.
An epiphany is a realization, a deep insight that a character in the story has or that the reader has.
As soon as this payoff is given (this article is ending with a summation) the story is over.