As I understand, the SSZ was introduced in Ethereum 2.0 for the serialization of data in different contexts. The previously used serialization is RLP and it is used when making a JSON-RPC request to an Ethereum node.
When moving to Ethereum 2.0 care was taken to be backward compatible so I presume that JSON-RPC requests are still done with RLP. To whom is the SSZ relevant? Is it only to the Ethereum nodes themselves for their internal data structure?
