How does the server determine when to access the database and when to use the cache?

The server typically uses cache to speed up access to frequently requested data and reduce the load on the database. The logic for choosing between cache and database can be as follows:

1. When a request is made, the server first checks if the required data is in the cache.
2. If the data is present (cache hit), the server returns it directly without accessing the database.
3. If the data is not present (cache miss), the server accesses the database, retrieves the data, stores it in the cache for future requests, and returns it to the client.

Thus, the server decides when to access the database based on the presence of data in the cache and the cache update policy (e.g., cache lifetime or invalidation upon data change).