In reply to Rain Johanson.

@Rain - good to hear from you :)

On inter-DC replication: yes we are relying on the replication capabilities of the DB itself. A few of these (eg.., Redis) are used strictly for transient data like caches and thus dont do inter-DC replication.

On chaos monkey: we typically run our entire battery of integaration tests on the production network, constantly. This is primarily functional testing, not the destructive testing that chaos monkey does. Running integration tests on production has been a frequent source of finding outages (though typically lots of other alarms are going off too). We're working towards a fuller Simian army type of testing but arent there yet.

Inter-service authentication is entire OAuth based. All inter-service comms is via REST, there are no backdoors.

Discovering the right media service to use: this is an evolving story and we're going to be taking a big step soon in an upcoming push; stay tuned :)