Scuba: Diving into Data at Facebook [pdf]

The article focuses a lot on the implementation, but thankfully you don't need to worry about that when using it. The flexible/quick/easy UI is what seals the deal for me, combined with the fast query times and realtime data -- you can use it to query things that happened literally seconds ago. On the React team we use it to collect all dev-time JS warnings from React that our engineers see so that we can easily track what the most high-firing messages are and how frequently they occur.

I haven't tried them extensively, but honeycomb.io and Interana are both Scuba-inspired products by ex-Facebookers. If this tool sounds at all interesting to you, I'd definitely look into using them.

^ This is Google's equivalent (mentioned at the end of the paper in "Related Work")

At Parse I was able to diagnose some seriously complex performance issues for customers by breaking splitting queries (precomputed in logs) into families and looking at probability distributions. It was amazing. Every time the customer told me XYZ was the problem I could send them a screenshot and refocus the conversation where the data sent us.

Some ex Parse employees left FB to build a visualization tool based on the same white papers (honeycomb.io). I'm really hoping to add that to my tool belt again.

I'd also like to echo what spicyj said about the UI, it is very usable. It was common for managers, PMs, and even people in completely non-technical business roles to use Scuba. It was my favorite internal product at FB and the one I miss the most.