We all want visibility into a running application. The need becomes acute when the application is ailing and that visible schedule, map, and cartogram of the data and processing will swiftly guide you to the failing part.
What is less recognized is that these same visuals are needed in maintenance. Your original, high performing developers are unlikely to be around after the application has been in production for a few years. They will have moved on to new green pastures. If you are lucky and they are still with the company then they will be somewhat available to the maintenance developers. If a little cantankerous about that.
The maintenance developer usually has little broad knowledge of the application’s operation. Her first task at resolving an application’s ailment will be to find suitable entrance and exit points. This is not an easy task for our applications now run continuously, across multiple processes and hosts, and are highly asynchronous. Hopefully, those high performing developers adhered to standards, used a common framework throughout, and kept to best-of-class external libraries and supporting tools. If they did then she might have a straightforward resolution path. In all likelihood, however, those high performing developers probably invented too much and documented too little. [I speak from the experience of my younger self.]
What the maintain crew needs is not logs alone. They need meta tools that connect to the running application and visually show its operation. Once connected the tool must be able to slow down the application to a human pace. Restrict it to one active user at a time. It might even need to switch it to run synchronously.
These are not easy features to implement, but the cost of not doing it is not just the ever lengthening backlog of ailments to fix, but the erosion of customer confidence and, in the end, loss of customers.
All modern applications have three users. The first is the customer. The second is the customer support. The third is the maintenance crew. It is way past time that the maintenance developer is provided the meta tools needed to look inside the running application and keep it fit for market.