DEV: (MOD-9575) memory reporting updates (#1508)

* DEV: (MOD-9575) memory reporting updates

* Apply review comments.

* Apply more review comments

* Apply more review comments

Author: dwdougherty

content/commands/json.debug-memory/index.md

@@ -35,6 +35,10 @@ title: JSON.DEBUG MEMORY
 ---
 Report a value's memory usage in bytes 
 
+{{< warning >}}
+The actual total memory consumption by a key could be much lower than the value reported by this command because of an internal JSON string reuse mechanism. For more information, see the [JSON memory usage page]({{< relref "/develop/data-types/json/ram#json-string-reuse-mechanism" >}}).
+{{< /warning >}}
+
 [Examples](#examples)
 
 ## Required arguments

content/develop/data-types/json/ram.md

@@ -123,3 +123,12 @@ JSON. The _MessagePack_ column is for reference purposes and reflects the length
 
 > Note: In the current version, deleting values from containers **does not** free the container's
 allocated memory.
+
+## JSON string reuse mechanism
+
+Redis uses a global string reuse mechanism to reduce memory usage. When a string value appears multiple times, either within the same JSON document
+or across different documents on the same node, Redis stores only a single copy of that string and uses references to it.
+This approach is especially efficient when many documents share similar structures.
+
+However, the `JSON.DEBUG MEMORY` command reports memory usage as if each string instance is stored independently, even when it's actually reused.
+For example, the document `{"foo": ["foo", "foo"]}` reuses the string `"foo"` internally, but the reported memory usage counts the string three times: once for the key and once for each array element.