[malandrew]

While I can agree that scala/java/jvm deserve some credit for this (typing, concurrency support), I think stories like this do a disservice in that they underestimate the importance of building a system a second time with all the lessons learned the first time around.

This is not unlike those stories where a developer writes a trivial program in a new language that is similar to a trivial program they wrote in another language 1+ years prior and compare the results. "I wrote program foo in 30 lines of code in language X, which is much better than the 120 lines of code it took me in language Y two years ago". It's natural for a developer to write a shorter program two years later since they have 2 more years under their belt. In fact I'd expect the same program to be much better two years later even if written in the same language.

[46Bit]

Very true. Twitter may have had a lot of scaling trouble, but that didn't necessarily mean moving everything onto the JVM was necessary to 'make it scale'. It was just sensible to pick a language that would prevent problems in future.

[ww520]

But if the second design is the better design theory has any impact, Twitter would have done better to build the second design with Ruby.