We're on Django; there is a relational DB in our architecture, but when you're browsing the site you're nearly always hitting either Solr or a key-value store.

We're on Django; there is a relational DB in our architecture, but when you're browsing the site you're nearly always hitting either Solr or a key-value store. But why wouldn't you use a relational database? It works, the ORM's good, it's fast enough, you're probably not going to hit scaling problems. If you do hit scaling problems, then that's a really really good problem to have.