Reads and Writes

In Cassandra, writes are much faster than reads, because of the way they happen.

Writes go to a "commit log" or "journal", in memory. Then they go into a table, also in memory. Finally they are flushed to SSTables and written to disk permanently.

All writes are sequential, which is partly what makes them so much faster.

Reads are slower because they need to find where the data is, find the node, find the data, and then find if it is in memory (or load it from disk if it isn't!).

Adding nodes

Adding nodes is good, as it increases replicas of data and thus resilience. Make sure your ring is balanced, as Cassandra does not like unbalanced rings.