Explanation/Reference:
In a write-through cache, every write to the cache causes a synchronous write to the backend store.
In this approach, the data is updated in the backend data store, then the primary cache, all within the scope of the transaction.
Then the backup cache is also updated to maintain consistency of data.
Incorrect answers:
In the refresh-ahead scenario, the cache is automatically and asynchronously refreshed before its expiration. The asynchronous refresh is only triggered when an object that is sufficiently close to its expiration time is accessed. If the object is accessed after its expiration time, a synchronous read from the cache store will be performed to refresh its value.
In a write-back or write-behind cache, writes are not immediately mirrored to the store. Instead, the cache tracks which of its locations have been written over. The data in these locations is written back to the backend store when those data is evicted from the cache.
In a read-through cache, if the data is not found in the cache, it is fetched from the backend data source, placed in the cache, and finally returned to the caller.
Reference: Oracle Reference Architecture, Application Infrastructure Foundation, Release 3.0