An edge dictionary is a key-value data store accessible to VCL during request processing.
Dictionaries comprise two primary parts: the dictionary container, and the items within it. Once you attach a dictionary container to a version of your service and that service is activated, the data in the container (the dictionary items) becomes "versionless." This means that any updates to the items will take effect immediately, without requiring a new version of the service. We also expose a separate dictionary info resource to report up to date metadata about your dictionary.
To find out more about using dictionaries in your service, see our help guide.