> Comment from that issue: "For example, ElasticSearch returns a 8,683KB document, I deser it into Value and the next RAM reading gives me delta of 98,484KB of RAM use. That's more than 10x the original size."

I think this is misleading. `serde_json` is designed to parse JSON documents directly into your user-defined structs. Thus the raw `Value` type isn't optimized for direct manipulation.

That said, what do you expect? The `Value` enum has the `Value::Array` variant that contains a `Vec<Value>`, which is 24 bytes in itself. One for the heap pointer, one for the length, and one for the capacity. Because of alignment requirements the enum discriminant must thus also be aligned at the 8-byte boundary. This gives us a 32-byte type.

It is possible to reduce the variant to 16 bytes by making the value type `Box<[Value]>` instead. Ignoring the `Value::Object` variant for a second, that would make `Value` a 24-byte type. However, you've now also made the type immutable. It's a tradeoff. 8 bytes for mutable values.

Again, do remember that deserializing into `Value`s is _not_ the primary path when working with JSON through `serde_json`.