Types of cache invalidation. Which ones do you know and have used?

Cache invalidation is the process of removing or updating outdated data in the cache to ensure the information remains current. The main types of invalidation are:

• Time-to-Live (TTL): the cache automatically resets after a specified lifespan. Used for data that changes periodically.
• Event-based: the cache is reset when a specific event occurs, such as data updates in the database.
• Manual invalidation: the developer explicitly triggers cache clearing or updating.
• LRU (Least Recently Used): the cache is automatically cleared when a size limit is reached, removing the least used entries.

In practice, TTL is most often used for HTTP response caching, and manual invalidation is used when updating database data to avoid serving outdated information.