You could use `in_batches` that way, but in the code from the article it looks like each call to `maximum`/`minimum` is causing a round trip, plus the `map` ins

You could use `in_batches` that way, but in the code from the article it looks like each call to `maximum`/`minimum` is causing a round trip, plus the `map` inside `MyService` is loading each batch into memory.