Let's say the server stores each particle as its constituent information (i.e. a JSON of attributes like 'position') and the client stores each particle as a sprite for rendering.
How should the entities be stored collectively? Maybe a JSON with randomly generated keys? In an array, the index of the server particle would have to line up exactly with the index of the client particle, which might cause problems when adding/removing elements (lag), but a JSON would not require this. What is the fastest reliable way to store entities across the server/clients?