After updating a row in the database, why do most cache-aside systems delete the cache key rather than write the new value into it?

Options

• ✓ Two concurrent writers can set the cache in the wrong order and leave the older value there; a delete cannot Correct
• ✗ Deleting a key is faster than writing one
• ✗ Caches cannot overwrite an existing key
• ✗ Deleting keeps the hit rate higher

Why

If writer A updates the database then writer B does, but B's cache write lands first and A's second, the cache keeps A's old value until the TTL ends. After a delete, the next read loads whatever the database holds now.

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