I took the article as to be more a case of using Redis as an example of a system which is reaching the limits of performance _given the current state of the kernel it's running on_, rather than a direct comment on the performance of Redis itself.

Also, saying that using Redis is slower than using a local hash table is a truism. There are myriad reasons why using a local, in-memory data structure is not viable: scalability and persistence, for example. It's like saying "I don't need a database, I can store everything in a local variable."