Can you explain the concept of two-level caching and its main purpose?

Two-level caching is an approach where data is cached at two different levels to improve performance and reliability.

Typically:

• The first level is a fast, local cache (e.g., in the application's memory).
• The second level is a slower but shared cache (e.g., a distributed cache like Redis).

The main purpose is to reduce data access time and decrease the load on the database or other sources.

Example: When data is requested, the local cache is checked first; if not found, the distributed cache is checked; if still not found, the database is queried. Once data is retrieved, it is stored in both caches.

This increases request processing speed and application scalability.