Do you really need that relational DB?

Do you really need that relational DB?

Say you're working with a big e-commerce project. From early days - you knew that normalised DB is the way to go and that's what you do nowadays. One day, the marketing department makes an amazing deal and your website is swarmed by thousands and thousands of customers! That's awesome! Except your DB is sweating so hard that in 2 minutes it releases the last breath and your caches expire. Now what?!

I had this crazy idea, deep in my mind, which no sane person believed in - perhaps we don't really need to query all those relations all the time? Perhaps there is a different way of modelling data for high load? If caching is so hard, are we doing it correctly? I'd like to share this idea with you, with some practical examples from production and theoretical guesses. My goal is to seed new ideas into your minds, feed them with a different approach which you might implement in the future. I'll be talking about data projections, events, queues, data modelling, and de-normalisation. Might mention a buzzword or two like NoSQL, AWS or DDD.