In a bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Mix until well combined.

Press the crumb mixture into the bottom of jars or glasses to form the crust layer.

In a large mixing bowl, beat softened cream cheese until smooth.

Gradually add sweetened condensed milk, key lime juice, and lime zest to the cream cheese, beating until smooth and creamy.

In a separate bowl, whip the heavy whipping cream and powdered sugar until stiff peaks form.

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

Spoon the key lime cheesecake filling over the prepared crust in the jars.

Refrigerate the jars for at least 2 hours, or until the cheesecake is set.

Garnish with lime slices and additional graham cracker crumbs before serving, if desired.