Over the years I think I've encountered more pain from applications where the devs leaned on denormalization than from those that developed issues with join performance on large tables.

You can mash those big joins into a materialized view or ETL them into a column store or whatever you need to fix performance later on, but once someone has copied the `subtotal_cents` column onto the Order, Invoice, Payment, NotificationEmail, and UserProfileRecentOrders models, and they're referenced and/or updated in 296 different places...it's a long road back to sanity.