What's the current state of NoSQL ?
simonw: NOSQL = Not Only SQL - I don't think you should ever expect it to completely replace SQL since they're good at different things. I've played with a bunch of NOSQL engines (including CouchDB, MongoDB, App Engine, Solr, Xapian and Tokyo) and while I really like them and would use them for a bunch of problems, for most of my projects the ability to create arbitrarily complex queries using joins is essential for rapidly iterating and trying out new ideas.Instead, I'd suggest using NOSQL stuff to complement SQL. Songkick use MongoDB as a fast caching layer for example: http://effectif.com/ruby/manor/denormalising-your-rails-appl... - and I've found Redis incredibly useful as a way of handling write-heavy parts of my applications and dealing with requirements to return random elements.One of the most interesting aspects of document stores such as CouchDB is that they are schemaless, which for some problem sets is incredibly powerful - anything where you might be tempted to use key/value pairs in SQL for example.