Can you explain the working principle and the purpose of cache systems in applications?

Cache systems are used to speed up data access and reduce the load on primary data sources (such as databases or external APIs). The principle of cache operation is that on the first request, data is retrieved from a slow source and stored in a fast storage (cache). For subsequent requests for the same data, the system first checks the cache and, if the data is there (cache hit), it returns it immediately, bypassing the slow source.

Goals of using cache:

• Accelerate application response
• Reduce load on the database or external services
• Increase system scalability

For example, if a web application frequently requests the same data, cache allows not to make repeated heavy requests to the database, but to quickly return the stored results.