Zookeeper slows down when you add nodes since quorum/consensus is larger. You can mitigate some of this with non-voting nodes (observer nodes) but only up to ce

Zookeeper slows down when you add nodes since quorum/consensus is larger. You can mitigate some of this with non-voting nodes (observer nodes) but only up to certain extent. So yes, a single Zookeeper cluster won't scale horizontally. But that doesn't limit the amount of independent clusters you can have. The reason I suggested Zookeeper is because it offers you ephemeral nodes, which is convenient to mark stuff as unavailable.