Cache
A cache is a fast temporary storage area that stores frequently accessed data to speed up access to that data. Caches are used in hardware (e.g., CPU cache) and software (e.g., web browser cache) to improve performance or reduce system load.
Reasons for considering a cache:
- Fast access to frequently accessed data
- Reduces latency and loading times
- Reduces load on other systems
- More efficient use of resources
Further information
Link: What is a cache
Possible Problems with Caching
| Challenge | Problem | Possible Solution |
|---|---|---|
| Consistency | Cache shows stale data | Write-through, event invalidation |
| Invalidation | When should the cache be updated? | TTL, LRU, LFU |
| Right strategy | LRU, LFU, or FIFO? | Choose depending on the application |
| Storage space | Too much data in the cache | Limited size, Redis/Memcached |
| Cache warmup | Cache starts empty | Preloading, persistent cache |
| Cache storms | Too many requests on cache miss | Locking, asynchronous loading |
| Security | Sensitive data in the cache | Encryption, private caches |
Cache Strategies
How a cache is used depends heavily on the use case. Depending on the requirements, there are several strategies for implementing the cache.
LRU - Least Recently Used
LRU (Least Recently Used) is a mechanism that removes the least recently used items to make room for new items. It is commonly used in operating systems, databases, and web caching systems.
LFU - Least Frequently Used
LFU cache (Least Frequently Used) is a mechanism that removes the least frequently used item when the cache is full.
FIFO - First In, First Out
FIFO (First In, First Out) caching is a simple mechanism that removes the oldest item once the cache is full. To put it simply, it works like a queue: the first item added is the first to be deleted.
LIFO - Last In, First Out
LIFO (Last In, First Out) caching is a mechanism that removes the most recently inserted element first when the cache is full. It works like a stack: the most recently added element is removed first.
Content Delivery Network (CDN)
A geographically distributed system for delivering (usually static) content. Content is delivered from a location as close as possible to the client. This minimizes response and loading times. Another advantage is that it acts as a cache, reducing the load on the actual servers behind it.
Please note
- Cache expiry: When to fetch the latest version of the content?
- Failover: What to do if the CDN goes down? (Forwarding requests to the server).
- Versioning of content.