In the usual case, Erlang does not use a contiguous chunk of memory to represent a sequence of bytes. Instead, it something called an “I/O list” — a nested list

In the usual case, Erlang does not use a contiguous chunk of memory to represent a sequence of bytes. Instead, it something called an “I/O list” — a nested list of non-contiguous chunks of memory. The result is that concatenating two strings (I/O lists) takes O(1) time in Erlang, compared O(N) time in other languages. This is why template rendering in Ruby, Python, etc. is slow, but very fast in Erlang. This sounds like it may break cache coherence? Template rendering in Erlang may be faster than Ruby & Python but I suspect using non-contiguous blocks of memory isn't the reason.