This is based on what? They have stated in various presentations that they have customers using 1pb clusters.
There's a re:invent presentation of them having an in-house 1pb+ cluster. What they don't tell you is that 101 8xl nodes is half a million dollars a year in reserved instances, before you include any other costs associated with it; and that particular workflow (log scanning) is very nicely suited for any columnar store.
Operations are also a disaster with Redshift; anything where you have to touch the cluster itself at any scale past a handful of nodes typically requires a support ticket with "hey, when this breaks, please work your magic and fix it?" There's also the issue of tuning your queues, which is a whole extra layer that you, the customer, must tune. Their suggestion tools are getting better on that front though.
Just use something else if you have more than a few TB, or you have a ton of time and money to just throw around.
As for ops stuff, I guess YMMV. We’ve never had any significant issues. Tuning is the same or less than on-prem systems IME.
Perf is still pretty much unmatched in the cloud, especially perf/$. Try to do a join on 100tb in a competing system (e.g. BQ) and it won’t finish.
(Disclaimer: I'm the lead of Debezium, which is the open-source CDC platform to which WePay are contributing their Cassandra work)
We are an AWS aligned consultancy who are seeing lots of take up of Aurora as it’s MySQL API compatible but with better performance and fully managed.
There’s an interesting pattern here using Lambda for CDC between Aurora and Redshift, though not sure how the cost would scale at WePay scale https://aws.amazon.com/blogs/big-data/combine-transactional-...