Sometimes dividing tasks creates inefficiency. When one person both cooks and cleans, they tend to create less washing up than if the tasks are divided, because washing becomes “somebody else’s problem”. However, when one person washes and the other dries, the load is equivalent. This setup can be prone to stoppages when the drainer is empty and the washer is trying to get that stubborn burnt bit off the pan, at which point any good ToC practitioner will ask the drier-upper to help with the washing to maintain throughput.
When teams are divided by layer instead of features, the interface between them becomes a fracture because each team has context missing from the other. Data has the wrong shape, validation requires fields that can’t be captured. If you build both sides, the transition is smooth.
When developers test, they can focus on smaller, independent chunks, which means fewer tests with greater coverage. Writing integration tests for complex calculations is painful and slow. Testing those same calculations as an xUnit Theory is cleaner and faster.
Specialists are great, but where is specialisation causing fractures and more work?