The Cassandra read path is somewhat more complex. Similar to the write path, structures in-memory and on-disk structures are examined, and then reconciled:
Figure 2.4: An illustration of the Cassandra read path, illustrating how the different in-memory and on-disk structures work together to satisfy query operations
As shown in the preceding figure, a node handling a read operation will send that request on two different paths. One path checks the memtables (in RAM) for the requested data.
If row-caching is enabled (it is disabled by default), it is checked for the requested row, followed by the bloom filter. The bloom filter (Ploetz, et-al 2018) is a probability-based structure in RAM, which speeds up reads from disk by determining which SSTables are likely to contain the requested data.
If the response from the bloom filter is negative, the partition...
