At past jobs I’d estimate we had 100 different production apps that in some way were powering key production systems. Sure some were backend/internal apps while others key production apps such as the dashboard itself. At other companies we had a smaller handful of Heroku apps that powered our cloud service, about 5-10 in total. Even just working with those internal apps it’s a number of things to keep context on. But when it comes to interacting with something you don’t know getting a lay of the land quickly is key. In helping a customer optimize and tune, or even just understand what is going on in their app an understanding of the data model is key.
As I just started a few months back at Crunchy Data I found myself digging into a lot of new systems and quickly trying to ramp up and get a feel for them.