Conversely, if a bomb goes off at the end of the story, chances are that bomb is in large measure what the story's about, and it must be planted, ticking, early in the story. Don't be overly predictable. Irony is an essential ingredient of plot construction. Irony at the plot level is the unexpected event that makes perfect sense. The beginning of a story has to make the reader want to read the middle of the story.
Conflict is an absolute necessity of fiction short or long.
The short story assumes there are obstacles to overcome, differences to reconcile, winners vs. losers, good guys vs. bad guys, inner struggles, arguments, fistfights, car chases, or merely difficult decisions. Mild or major, the conflict is at the heart of both character and plot. And somewhere in the plot, this conflict often results in a significant shift in the balance of power. A character must make a choice, and because of that choice, the character changes. Built into that last statement is the concept of consequence.