What is the role of SSTables in the context of Cassandra?

SSTables, or Sorted String Tables, play a crucial role in Cassandra's architecture as they are designed to efficiently handle the storage and retrieval of data. They hold consolidated versions of data in a read-optimized format, allowing for quick reads and efficient use of storage. This optimized format results from the merging and compaction of data written to disk, which enhances performance by reducing the need to access multiple data files.

The structure of SSTables allows for fast lookups since they are sorted by row keys, making it easy to locate the data quickly. Moreover, because SSTables are immutable, once data is written, it does not change, which means that there is no need for locks during read operations, improving overall performance and scalability.

The other options do not accurately capture the primary function of SSTables in Cassandra. For instance, while transaction logs are important in Cassandra for durability during write operations, SSTables serve a different purpose focused on data storage and retrieval efficiency. In addition, SSTables are not limited to security implementations or real-time data processing. They are a fundamental part of the way data is structured for optimal access and performance in this NoSQL database system.