Minor quibble: The difference between static files and memory based caching is minimal. Any server OS will cache "hot" files in RAM, so in day-to-day use the

Minor quibble: The difference between static files and memory based caching is minimal. Any server OS will cache "hot" files in RAM, so in day-to-day use the difference between nginx serving up static files from disk, or hitting memcached is pretty minimal - it's just a question of which part of the stack is caching your content in RAM. Caching, in general, is famously a very hard problem however, and prone to special corner cases. :) Your larger point is correct.