Cassandra Practice Test

During a read operation in Cassandra, what does the Bloom filter help achieve?

1. It retrieves data from Memtable efficiently

2. It checks if a requested partition does not exist in an SSTable

3. It manages the sorting of data

4. It maintains the integrity of the commit log

The correct answer is: It checks if a requested partition does not exist in an SSTable

The Bloom filter is a crucial data structure used in Cassandra to optimize read operations. Its primary function is to quickly determine whether a specific partition key is likely to be present in a given SSTable (Sorted String Table) or definitely not present. When a read request is made, the Bloom filter allows Cassandra to efficiently check against each SSTable to avoid unnecessary disk I/O operations, drastically improving read performance. If the Bloom filter indicates that a partition key is not present in the SSTable, Cassandra can skip that SSTable during the read operation, saving time and resources. This capability to filter out SSTables that do not contain the requested data plays an essential role in Cassandra's design, as it enhances the system's ability to handle large volumes of data with speed and efficiency. The other options do not accurately describe the function of the Bloom filter. While data retrieval from the Memtable is achieved through other mechanisms, the management and integrity of the commit log are handled separately. Sorting of data is also managed via the SSTables and their organization, rather than by the Bloom filter. Therefore, option B correctly reflects the purpose of the Bloom filter in read operations within Cassandra.