I am pretty used to people defending their blind trust in big-O notation. As I mentioned, the idea is to be open to alternative ways of thinking. Performance

I am pretty used to people defending their blind trust in big-O notation. As I mentioned, the idea is to be open to alternative ways of thinking. Performance is incredibly difficult or impossible to generalise. I have many times worked on a project where people said confidently it is not possible to speed something up and then I speeded it up by multiple orders of magnitude. I worked for one of largest banks in the world and we had a batch task on MongoDB that took 12 hours to complete. The previous team, before I joined, took it down to 4 hours but then said it is not possible to improve it anymore. The consultants from MongoDB confirmed it. This was a huge problem because there was a delay of 4 hours between end of trading day and the report being finished which was unacceptable. I took it down to ~15 seconds. Without changing data structure or the database or the application technology. The only significant thing I did is I made both the data suppliers to stream it to our app and the consumers to stream the results during the data. So the data was being processed during trading day and partial results were already being pushed to the client. The only thing that needed to be done was to sync between the sources and the clients and it took about 15 s to do it (and I could probably take it even further but it was not worth the effort). So you see, it is all about being open minded.