I'm an engineer by trade. I rely on intuition when investigating a slow Django app. I've solved a lot of performance issues over the years and the short cuts my brain takes often work. However, intuition can fail. It can fail hard in complex Django apps with many layers (ex: an SQL database, a NoSQL database, ElasticSearch, etc) and many views. There's too much noise.

Forecasting traffic to your web app is important for capacity planning, but generating a seasonally accurate model of your traffic is pretty daunting.