I don't think there was sufficient room in the article to cover the value of sub-transactions, let alone transactions as a whole. In this case I think it's fair

I don't think there was sufficient room in the article to cover the value of sub-transactions, let alone transactions as a whole. In this case I think it's fair for it to be assumed knowledge given the contents of the article. They are definitely not pushing the limits of PostgreSQL as a whole, they just hit an edge case with a not heavily used feature. Sub-transactions aren't overly common in most PostgreSQL workloads I have encountered, especially not coupled with long-running transactions. Great write-up though! I do hope patches to make the sub-transaction cache configurable land, while it's not something I have ran into it would be a great lever to have if I do.