Great write up. This will be a good point of reference for future debates concerning the value of selecting high-performance platforms for web-applications. A common refrain among advocates of slower platforms is that computational performance does not matter because applications are invariably busy waiting on external systems such as databases. While that may be true in some cases, database query performance is often only a small piece of an overall performance puzzle. Blaming external systems is a too-convenient umbrella to avoid profiling an application to discover where it's actually spending time. What to do once you've made external systems fast and your application is still squandering a hundred milliseconds in the database driver or ORM, fifty milliseconds in a low-performance request router, and another 250 milliseconds in a slow templater or JSON serializer?
Yes, three seconds for a page render is still uncomfortably slow, but it's substantially faster than the original implementation, and unsurprisingly frees up CPU for additional concurrent requests. It's a shame Wikimedia didn't have this platform available to them earlier.
Today web developers have many high-performance platform options that offer moderate to good developer efficiency. Those who use low-performance platforms may do their future selves a service by evaluating (comfortable) alternatives when embarking on new projects.