You implement 'Traffic Mirroring' at the Gateway to test a new Payments Service (v2) with live traffic. Why must you ensure the v2 service is 'Sandboxed' or 'Mocked' for downstream side effects?

1. A Because mirroring traffic doubles the bandwidth cost of the Gateway, which could lead to billing overages.
2. B To prevent 'Side Effect Leakage': If the shadow service is live, it might unintentionally send real duplicate emails, process real credit card charges, or corrupt production data while it 'tests' the request.
3. C Because mirroring only works if the v2 service uses the exact same IP address as the v1 service.
4. D Mirroring traffic is illegal under GDPR unless the user explicitly opts into the shadow test.