i originally said pricing for other managed sql dbs, not specifically “serverless” ones. we both know that is just a marketing term anyway

with ACUs the point is you configure min and max, and your cluster scales up/down based on a cpu utilization threshold. so, sure reading from memory uses cpu cycles — but a large cached read is incredibly unlikely to bump you over a scaling threshold which affects your bill, unless you’re doing some huge heavy sort operations

another key point is aurora serverless v2 does not scale down to 0 acu. you are always paying a predictable small amount for your base cpu and ram. minor increases in cpu usage literally do not impact your bill at all, which is why i do not believe your argument makes sense regarding cached reads.

edit to add: the reason this matters for monetary cost of ELT/ETL is it often involves very large reads. if your jobs only extract recent/changed data, this will very likely be in buffer pool, and cost way less with io pricing than with your row based pricing. clear?