Stir together the graham cracker crumbs, sugar, and melted butter until evenly moistened. Press the mixture firmly into the bottom and about 1 inch up the sides of a greased 7-inch springform pan. Place the pan in the freezer while you make the filling.
Beat the softened cream cheese and sugar with an electric mixer on medium speed until completely smooth, about 3 minutes, scraping down the sides as needed. Beat in the eggs one at a time on low speed, mixing just until each is incorporated.
Add the sour cream, vanilla extract, and flour to the batter. Mix on low speed until just combined. Do not overmix. Pour the filling into the prepared crust and smooth the top with a spatula. Cover the pan tightly with aluminum foil.
Pour the water into the Instant Pot and place the trivet inside. Create a foil sling by folding a long piece of foil lengthwise into a strip. Set the cheesecake pan on the sling and carefully lower it onto the trivet.
Lock the lid, set the valve to sealing, and cook on high pressure for 35 minutes. When the cook time is done, let the pressure release naturally for 10 minutes, then carefully turn the valve to venting to release any remaining pressure.
Lift the cheesecake out using the foil sling. Remove the foil cover and gently blot any moisture on top with a paper towel. Let it cool on a wire rack at room temperature for about 1 hour.
Cover the cheesecake loosely and refrigerate for at least 6 hours or overnight. Once fully chilled, run a thin offset spatula around the edge, release the springform ring, slice, and serve.