What does system resiliency refer to, and how would you achieve this here at Amazon?

"A system is considered resilient if it can continue to function even though other parts of the IT infrastructure have failed or are no longer available. This is especially important in mission-critical systems, which perform functions important to the operations of the organization. Some of the methodologies I would use to ensure system resiliency at Amazon include redundancy, backups, isolation, delegation, and containment. Reducing the impact of any system failure and preventing it from spreading to other systems is key to maintaining high availability and keeping Amazon's business processes functioning."