When is it worth optimizing database queries versus scaling vertically?

hey everyone, ive been thinking a lot about database performance lately. weve got a few queries that are starting to get pretty slow under load, and my instinct is to optimize them. but another part of me wonders if its just easier to throw more resources at the database server, vertical scaling. what are your thoughts? when do you prioritize query optimization, and when do you just scale up? what are the trade-offs you consider?