Whisk soy sauce, oyster sauce, rice vinegar, sesame oil, brown sugar, Sriracha sauce, and garlic in a small bowl until smooth.
Pour sauce into a multifunctional pressure cooker, such as Instant Pot. Stir in shrimp. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 0 minutes. Allow 10 minutes for pressure to build.
Meanwhile, whisk cornstarch and cold water together until smooth.
Release pressure carefully using the quick-release method according to the manufacturer's instructions, about 2 minutes. Unlock and remove the lid. Stir in cornstarch slurry and broccoli. Select Sauté function and cook until sauce thickens and broccoli is crisp-tender, about 2 minutes.
Garnish shrimp and broccoli with green onions and sesame seeds.