> If you had a million of them to process thats 4 hours

If you had 20 bank accounts sending you monthly statements for 100 years you'd have 24,000 of them. 50ms each would take you 20 minutes to process the 100 year backlog.

If you have a million of them to process then you're a bank or similar type of institution that can devote resources to this, either computational or developer time to optimize things. A 128 core c6a.32xlarge would turn the runtime from 4 hours into 1.9 minutes and cost $5 to run for an hour.