Graham Cracker Crust

In a food processor, chop the graham crackers with the sugar, cinnamon, and melted butter until it resembles wet sand.
Press the mixture into the bottom of a foil-lined 8×8-inch pan. Freeze while preparing the cheesecake filling.
Key Lime Cheesecake

In a medium bowl, whisk the heavy whipping cream until stiff peaks form.
In a separate bowl, stir the softened cream cheese until smooth. Mix in the sweetened condensed milk, key lime juice, and zest.
Carefully fold the whipped cream into the lime mixture just until combined.
Pour over the frozen crust, cover, and refrigerate overnight. For quicker setting, freeze for a few hours before cutting into bars.