=== Scale Horizontally

What about scaling as the demand for our application grows?((("scaling", "horizontally")))((("clusters", "three-node cluster")))((("primary shards", "in three-node cluster"))) If we start a third node, our cluster reorganizes itself to look like <>.

[[cluster-three-nodes]] .A three-node cluster--shards have been reallocated to spread the load image::images/elas_0204.png["A three-node cluster"]

One shard each from Node 1 and Node 2 have moved to the new Node 3, and we have two shards per node, instead of three. This means that the hardware resources (CPU, RAM, I/O) of each node are being shared among fewer shards, allowing each shard to perform better.

A shard is a fully fledged search engine in its own right, and is capable of using all of the resources of a single node. With our total of six shards (three primaries and three replicas), our index is capable of scaling out to a maximum of six nodes, with one shard on each node and each shard having access to 100% of its node's resources.