I'd like to read more about the backing data stores. If you're aggregating data across a lot of different stores, it seems you could easily add what looks like a tiny piece of data to your query, but, in truth, is much more expensive on the backend.
It's important to realize that you're essentially defining an API for your product. If something is expensive to access, you should either not expose it directly through your API, or add appropriate levels of caching to mitigate the costs.
