> There is no mutable state. Yes, there is. Appending a new log entry to the depot mutates the depot. It doesn't mutate earlier records in the depot, but the d

> There is no mutable state. Yes, there is. Appending a new log entry to the depot mutates the depot. It doesn't mutate earlier records in the depot, but the depot is the entire record set, not just individual records. The record set is different after the append than before it.