In this AWS re:Invent 2023 session, Adrian Hornsby and Iris from the AWS Reliability Team discuss the importance of application resilience and introduce new features of the AWS Fault Injection Service. They explain the high costs of downtime, the complexity of distributed systems, and the four pillars of resilience engineering. The presenters introduce the resilience lifecycle framework and demonstrate how to use fault isolation boundaries like Availability Zones and Regions to build resilient applications. They also showcase new scenarios for testing multi-AZ and multi-Region applications, emphasizing the importance of continuous testing and learning in maintaining application resilience.