What is the mechanism of action of aspirin?

Aspirin irreversibly acetylates and inhibits cyclooxygenase (COX-1/COX-2), blocking thromboxane A2 production in platelets for their entire ~7-10 day lifespan — this is its antiplatelet mechanism. Factor Xa inhibitors (like apixaban), vitamin K antagonists (warfarin), and direct thrombin inhibitors (like dabigatran) are all different drug classes with different mechanisms.