Hi @deepakp. There are 4096 partitions for each namespace. If you have a replication factor of 2 and 2 nodes in the cluster, each of those nodes has 2K master partitions and 2K replica partitions. You’ll never have the master and replica of the same partition ID on the same node. If you scale to 4 nodes, each node will have 1K master partitions and 1K replica partitions. For more see the architecture overview page on data distribution.
Aerospike scales well both horizontally, by adding more nodes, and vertically by adding more resources per-node such as drives. See the following FAQ:
Each node indexes only the records in the partitions assigned to it. Having double the nodes will reduce the memory usage of the primary index on each node to half what it was before. You can also scale vertically and double the DRAM per-node. See the Capacity Planning Guide.