replicas

You can also add up to 15 Amazon Aurora Replicas across three availability zones to further scale read capacity.

Most services are mastered at NYI, with replicas at other sites (currently Amsterdam, soon LA as well).

Our physical read replicas receive redo log records, update cached entries and have readonly access to the underlying storage tier.

Flying airplanes should be replicas, made as close to the original specifications as the owner wants.

For example, a few years ago there was a project at Paine Field to build flying replicas of the Me262.

It's more likely that some far dumber-than-human machine would replicate itself with full coordination over its replicas and wipe us out.

So, on a minimum three-node setup, three replicas + three shards per table are doable?

Because my brain replicas might very soon decide they don't want to play together.

I suppose that would also mean that if an outage takes out more than half of your replicas then you will loose all write-abilities That's correct.

We always require a majority of replicas to be present for any given shard before failing over the primary of that shard.

So to sustain a one node failure, you need three nodes and three replicas.

In our current architecture, we perform failover by selecting a new primary among the existing replicas for a given shard.

"Writes initially only happen on primary shards, and then propagate to replicas." - also true but you still want this to be as distributed as possible.

"Node A will degrade faster than the rest of the cluster due to extra CPU use, memory writes, and disk read/writes." Also, remember that you can scale reads using replicas.