The previous articles on Multitenant Applications talked about recovery and replication. This article talks about organization of data particularly keys and values.

Configuration data is stored as key-values. They are a simple and flexible representation of application settings. Keys serve as identifiers to retrieve corresponding values. A best practice involves organizing keys in hierarchical namespaces by using a character delimiter. A convention is not mandated for multiple tenants, but it helps. Keys regardless of their format must be treated as a whole. When parsing is avoided, it is easier to not break any usages. Data used within application frameworks might dictate specific naming schemes for key-values. A combined size limit of 10KB usually applies on a key-value.

Key namespaces must be easier to read with proper use of delimiters to denote hierarchical information. They must also be easier to manage. A key-name hierarchy must represent logical groups of configuration data. They should be easy to query using pattern matching.

Key-values can optionally have a label attribute. Labels are used to differentiate key-values with the same key. No labels are associated initially, and key-values can be referenced without a label.  A common use of labels is to denote environments for the same key. Labels can also be used to create versions. It is possible to jump forward or fall back between keys using versions. Values depend on content-type with Unicode as the most popular form.  MIME types are also applicable for feature flags, Key Vault references, and JSON key-values.

Key-values can be soft-deleted which means that they can be recovered. Soft delete will act as a safeguard to scenarios including the case when a deleted app configuration store could be recovered in the retention time period and the case when an app configuration store is permanently deleted. A soft-deleted store will be retained for a short time known as the retention period. When it elapses, the store is deleted permanently. Key-values can also be purged before the retention period expires. Permission to read and purge deleted stores are granted to owner and contributor roles by default.

Json content-type is preferable over other formats for key-values because it provides simpler data management, enhanced data export, and native support with app configuration provider. When configuration data changes, Event Grid can be used to receive data change notifications. These events can trigger web hooks, Azure functions, Azure storage queues, or any other event handler. Typically, a resource group and a message endpoint are created to subscribe to the topic.