In a medium mixing bowl, combine the graham cracker crumbs and sugar. Pour in the melted butter and stir until the crumbs are evenly coated and resemble wet sand. The mixture should hold together when pressed with a spoon.

Transfer the crumb mixture into a 9-inch pie dish. Press the crumbs firmly into the bottom and sides of the dish using the back of a spoon or the bottom of a measuring cup. Make sure the crust is packed tightly so it stays together after chilling.

Place the crust into the refrigerator while preparing the filling.

Add the softened cream cheese to a large mixing bowl. Beat with a hand mixer on medium speed until smooth and creamy with no lumps remaining.

Scrape down the sides of the bowl with a spatula to ensure even mixing.

Pour the sweetened condensed milk into the cream cheese mixture. Add the key lime juice, lime zest, and vanilla extract.

Mix until the filling becomes smooth, creamy, and fully combined. The mixture should look thick and silky.

Add the whipped topping to the bowl. Using a rubber spatula, gently fold the whipped topping into the lime mixture until fully combined.

Fold slowly to keep the filling light and fluffy. Avoid overmixing.

Remove the chilled crust from the refrigerator. Spoon the filling into the crust and spread evenly with a spatula.

Smooth the top gently while leaving soft swirls for a homemade look.

Place the pie into the refrigerator for at least 4 hours or until fully set. For best results, chill overnight before slicing and serving.

Before serving, top the pie with whipped cream, lime slices, extra lime zest, or graham cracker crumbs if desired.

Slice with a sharp knife and serve cold.