You work with Microsoft SQL Server, Azure SQL DB, and Amazon RDS SQL Server.
When people call in saying the server is slow, you’re the one who has to take the call.
It’s up to you to figure out the bottleneck, which queries are causing that bottleneck, what changes to make to the queries, and whether index or server-level tweaks can help.
You’ve done the best job you can with the free resources out there, and you’ve pushed all the easy buttons. You’re looking for more definitive answers, like polished techniques that have been used on clients around the world.