Predict & verify6 min·Module 1

Route the job

Predict before you look

Five tickets land on your desk. For each, pick the surface you would reach for first. Two of them are arguable on purpose; read the reasoning even when you get it right.

0/5

Which surface first?

ticket · from a teammate

"I ran EXPLAIN ANALYZE on the orders query and pasted the plan
 below. It's doing a seq scan on a 40M-row table. Before we
 touch anything, can you help me understand WHY the planner
 chose that, and what our options are?"

 [plan output pasted, 60 lines]