Kraken is a very decent exchange, but they do indeed happen to suffer from high intensity moments when the markets are quite volatile. It mainly happens because people are refreshing constantly, which causes a soft DDoS effect occasionally - this of course still doesn't justify them not allocating more bandwidth. Exchanges are very stingy when it comes to investing in more bandwidth, and Coinbase fits in that category as well, and that while they are by far the wealthiest crypto related business in this market. Bitstamp thus far has been working exceptionally well for me, even in periods where the volatility was reaching its boiling point.