Manigandham is exactly correct on the amount of RAM used by Aerospike per primary index entry. This is a primary factor in the correct sizing of a cluster.
ManuelSchmidt is right on the money about data modeling being crucial. You may not need 100billion records based on your data model. A primary key in Aerospike points to a Record, which can contain 1 or more fields called Bins, so you can store more that one value per key if this makes sens for your use case. He is also 100% correct on the use of secondary indexes. These give you a “query” capability but at a longer latency.
What you need to do is understand exactly your read/write throughput and latency needs to be to meet your SLA, and exactly what you need to store to satisfy your business transactions. Then model the data to suit those needs.
One tip on modeling for NoSQL: Stop thinking rows, columns and normal form - denormalize
The data model will be closer in structure to your heap variables (object graph or data structures) than rows and columns. Think of Aerospike as a huge associative array or hash table and then model accordingly.
I hope this helps