One box testing works well for some scenarios. It's not completely safe but the risks are low. If there is an issue then it only impacts a very small number of

One box testing works well for some scenarios. It's not completely safe but the risks are low. If there is an issue then it only impacts a very small number of customers. If they retry they'll likely hit one of the thousands of stable instances. Comparing metrics between the one box and normal instances is helpful and can be tied in to CI/CD for automatic rollbacks if necessary.