For those interested in how an ecommerce site stacks up with traffic spikes, Shopify did a great job, the weak link was paypal. We had a good number of (potential) customers email to us to say that paypal locked up during payment, we were taking several orders a minute for a while there but still annoying that some were dropped.

One of our mailing lists also grew by 1200 names in 3 hours and Mail Chimp coped fine.