I think TFA was more about "when to invalidate/recompute" than "how to invalidate/update" -- that you need to take care to enumerate all of the times the denorm

I think TFA was more about "when to invalidate/recompute" than "how to invalidate/update" -- that you need to take care to enumerate all of the times the denormalized value may get out of sync with the rest of the data. (This is a reasonable idea though, depending on access patterns. Can increase latency, can decrease computation.)