They already have full end-to-end tests. Which additional testing should they run to reduce risk of cloud-induced outages?

The correct answer is adding additional unit tests and production scale load tests on their cloud staging environment. While end-to-end tests verify overall functionality, they don't always catch performance bottlenecks or edge-case failures under realistic load. Unit tests isolate and validate individual components, preventing small errors from cascading into larger outages. Production-scale load tests on a staging environment simulate real-world traffic, identifying performance issues, resource limitations, and scalability problems before deployment to production, significantly reducing the risk of cloud-induced outages. Enabling Google Stackdriver Debugger is for debugging existing issues, not preventing them. Running existing end-to-end tests in staging is good practice but doesn't add new testing dimensions to reduce risk beyond what's already covered. Canary tests are for gradual rollout and monitoring impact of new releases, not for pre-deployment risk reduction of cloud-induced outages.