Heat the oil in a large wok or nonstick frying pan over medium-high heat. Add the onion and cook, stirring often, until it becomes soft and translucent, 3 to 4 minutes. Add the frozen vegetables and shrimp and cook, continuing to stir, until the shrimp begins to turn pink and opaque, or another 3 minutes. Add the garlic and cook, stirring, for another 30 seconds.
Use a wooden spoon or rubber spatula to move the vegetable mixture to one side of the pan. On the other side of the pan, add the beaten eggs and cook them, stirring constantly, until they are scrambled, about 2 minutes. Once the eggs are scrambled, mix them with the vegetables and then add the cauliflower rice, soy sauce and sriracha. Cook, stirring constantly, until the cauliflower rice softens, 3 to 4 minutes. Turn off the heat and stir in the green onions.
This dish can be served immediately or refrigerated, covered, for 3 to 4 days. It can be enjoyed either hot or cold.