Time at the bottleneck is what counts
Which of these feature ideas should we select?
Feature A? It's a no-brainer, right?
Not necessarily. The Theory of Constraints tells us that the overall throughput of our production pipeline is limited by the throughput of the bottleneck. That means if we want to squeeze as much value through our pipeline as possible we have to squeeze as much value through the bottleneck as possible. So what's important isn't the total time, but the time that each of the features takes at the bottleneck.
|Away from the
|A||$100,000||20 hrs||20 hrs||40 hrs|
|B||$80,000||10 hrs||30 hrs||40 hrs|
|C||$60,000||10 hrs||30 hrs||40 hrs|
In this case, for the same 20 hours at the bottleneck we can produce both B and C for a total of $140,000, compared with A at $100,000.
If you're not convinced, imagine the following scenario: You have 100 business analysts, 100 developers and 1 tester. All the work has to be tested by the tester. The tester is the bottleneck and everyone else spends most of their day sat around twiddling their thumbs. Obviously we want to do everything we can to off-load tasks from the tester onto other people. This is effectively what features B and C do, compared with A, because they require less time with the tester.