In the previous chapters, you learned about several patterns and technologies you can use to build secure, scalable, and resilient applications. However, we still lack visibility into the Polar Bookshop system, especially when something goes wrong. Before going to production, we should ensure our applications are observable and that the deployment platform provides all the tools needed to monitor and gain insights into the system.
Monitoring involves checking the telemetry available for the application and defining alerts for known failure states. Observability goes beyond that and aims at reaching a state where we can ask arbitrary questions about the system without knowing the question in advance. The product team should ensure their applications expose relevant information; and the platform team should provide an infrastructure for consuming that information and asking questions about their operations.