Security and resilience are two important aspects that should be considered when developing applications of any scale. Security protects an application's secrets, performs authentication, and provides authorized access to secure content, whereas resiliency embraces the application if it fails so that it can degrade gracefully. Resiliency makes an application highly available and allows the application to function properly at the time when an error occurs or when it is in a faulty state. It is widely used with the microservices architecture, where an application is decomposed into multiple services and each service communicates with other services to perform an operation.

There are various techniques and libraries available in .NET Core that we can use to implement security and resiliency. In ASP.NET Core applications, we can use Identity to implement user authentication/authorization, a popular Polly framework to implement patterns such as circuit breaker, the retry pattern, and others.

In this chapter, we will look at the following topics:

• Introduction to resilient applications
• Implementing health checks to monitor application performance
• Implementing the retry pattern in ASP.NET Core applications to retry operations on transient faults
• Implementing circuit breaker patterns to prevent calls that are likely to fail
• Protecting ASP.NET Core applications and enabling authentication and authorization using the Identity framework
• Using safe storage to store application secrets