What is a key feature of lightweight transactions in Cassandra?

Lightweight transactions in Cassandra are designed to permit conditional updates while ensuring atomicity. This means that you can perform updates to the database only if certain conditions are met, making them useful for scenarios that require strict data consistency. For example, if you want to update a record only if it currently has a specific value, lightweight transactions allow you to do this through the use of the "IF" clause in your query. This functionality is essential when concurrent modifications could otherwise lead to inconsistencies, as it enforces a check on the data before the update is committed, ensuring that the operation is atomic and either completely succeeds or fails without leaving the data in an intermediate state.

In contrast, the other choices do not accurately represent the key feature of lightweight transactions. They might refer to other benefits or functionalities within Cassandra, such as performance or storage concerns, but they do not encapsulate the primary characteristic of lightweight transactions, which revolves around their ability to handle conditional updates with atomic properties.