Cassandra Practice Test

What is the role of MemTable in data operations in Cassandra?

1. It is a permanent storage layer

2. It stores data temporarily before writing to the commit log

3. It handles read queries efficiently

4. It regulates data compaction processes

The correct answer is: It stores data temporarily before writing to the commit log

The role of MemTable in Cassandra is crucial in understanding how data operations work. MemTables are in-memory data structures that temporarily store write operations before they are flushed to the disk or the SSTable files. When a write operation occurs, the data is first written to the MemTable, which allows for quick access and performance benefits because it avoids immediate disk I/O. Once the MemTable reaches a certain size threshold, it is flushed to disk, at which point the data is also recorded in the commit log to ensure durability. This mechanism improves the efficiency of write operations, as many updates can occur in memory before being written to permanent storage. Therefore, the correct choice highlights the role of MemTable in managing temporary data before it is ultimately persisted to disk. The other choices address different components or processes within Cassandra. The permanent storage layer refers to the SSTables stored on disk, read query handling involves the coordination of various data structures including the SSTables and Bloom filters, while data compaction processes focus on the efficiency of data storage and retrieval but are not directly related to the MemTable's primary function. Thus, the emphasis on temporary data storage before the commit log accurately reflects MemTable's purpose in Cassandra's architecture.