There are two objects we use in all JSON interfaces. We use the TempBlob table and our custom JSON Interface Codeunit.
JSON interface uses the same concept as a web service. The endpoint is defined by the Codeunit Name and the caller always supplies a form of request data (JSON) and expects a response data (JSON).
These interface calls therefore are only internal to the Business Central (NAV) server and are very fast. All the data is handled in memory only.