The DX Core 4 is an opinionated developer productivity framework that provides clear and concise metrics for measuring developer performance. It takes a bold approach by stating exactly which metrics should be used, rather than offering a range of options or relying on theoretical approaches. The framework focuses on four key metrics: Speed (diffs per engineer), Effectiveness (Developer Experience Index), Quality (Change Failure Rate), and Impact (Time Spent on New Capabilities). These metrics create "productive tension" with each other, ensuring that organizations prioritize the right aspects of developer productivity. DX Core 4 is distinct from frameworks like SPACE and DORA, which offer more comprehensive theoretical models or technical metrics. The framework's emphasis on practicality and standardization makes it a valuable starting point for organizations looking to measure the value of their developers and improve their productivity. By providing a clear direction and enabling meaningful industry comparisons, DX Core 4 has the potential to bridge the gap between engineering metrics and business value.