There are a lot of database index and query best practices that sometimes aren't best practices at all. Need all users created this year? No problem! Slap an index over created_at! What about this year's active OR pending users, sorted by username? Are we still covered index-wise? Is the query as fast with 20 million users? Common rules of thumb for indexing and query crafting aren’t black and white. We'll discuss how to track down these exceptional cases and walk through some real examples. You'll leave so well equipped to improve performance, you won't be able to optimize fast enough!