In a medium bowl, combine graham cracker crumbs and melted unsalted butter. Mix until crumbs are evenly coated. Reserve ½ cup for later.

Press the graham cracker mixture firmly into the bottom of a trifle dish to form the crust.

Chill a mixing bowl and beaters, then beat the heavy whipping cream until stiff peaks form.

In a separate bowl, beat together softened cream cheese and powdered sugar until smooth, then add key lime juice, lime zest, and vanilla extract.

Gently fold the whipped cream into the cream cheese mixture until well combined.

Spread half of the creamy lime filling over the graham cracker crust.

Layer the remaining lime filling over the crumbs and top with additional reserved graham cracker crumbs and lime zest.

Cover the trifle and refrigerate for at least 2 hours before serving.