Guide: Understanding Amazon API Gateway Stages

API Gateway Stages are an essential part of the Amazon API Gateway. They represent the path through which an API deployment is accessible. They are a pointer to a deployment of an API and they also provide features like throttling, caching, logging, and adding permissions.

Importance:
It becomes crucial in managing and handling versioning and lifecycle of an API. With stages, you can manage different environments (like dev, prod, test, etc.) for the API's lifecycle. Stages also have individual settings for throttling, caching, data tracing, and logging for observability and to control the usage of your APIs.

Working:
When you deploy an API, you need to provide a stage. Existing stages can also be updated with new deployments. Stages get a unique Invoke URL. Stages can also hold stage variables, which are name-value pairs, wherein you can store configuration settings that your setup needs to execute APIs.

Exam Tips:
Understanding the relationship between stages, deployments, and stage variables is key. Remember to consider caching and logging settings at the stage level. Be sure to recognize the usage scenarios where stages would be useful. Always remember that stages represent a named reference to a deployment.

Answering Questions on API Gateway Stages:
Know the purpose of API Gateway stages and understand the use cases (like versioning, environment separation). Be familiar with the configuration settings and features provided by API Gateway at the stage level (like throttling, caching, logging). Understanding how stage variables are used to manage configurations can be very beneficial.