You're right that low DNS TTL is not perfect (we saw few providers that override the TTL to reduce the number of DNS queries going out of their network, this is a big hack but cause some trouble). This problem is addressed by our API clients that have different DNS endpoint to reach the 3 machines of a cluster.

We cannot use any local network IP or load-balancer as we distribute a cluster on several providers with different autonomous systems. This is how we are able to offer SLA of up to 99.999% with a big refund strategy: https://blog.algolia.com/for-slas-theres-no-such-thing-as-10...