Causes of Cache Stampede or Dogpile Problem

The cache stampede or dogpile problem can occur due to various causes. The following are some typical causes of this problem:

1. Cache expiration:

A cached resource must be refreshed when it becomes invalid after expiration. If multiple requests arrive simultaneously after the cache expiration, they all find the cache empty and trigger cache misses, leading to a surge in backend requests.

2. High contention:

In scenarios where multiple concurrent requests are accessing the same resource, such as a frequently accessed cache entry, the likelihood of cache stampede increases. As each request detects a cache miss, they all try to regenerate or populate the cache entry simultaneously, causing contention and potentially overwhelming the backend.

3. Synchronized cache invalidation:

If cache invalidation is performed in a synchronized manner, where multiple requests trying to invalidate the same cache entry block each other, it can lead to a cache stampede. As soon as the cache entry is invalidated, all the pending requests might simultaneously try to regenerate the cache, causing a surge in backend requests.

4. Time-based cache expiration:

When using a time-based expiration policy, such as setting a fixed cache duration for a resource, it increases the likelihood of cache stampede. If the cache duration is short, multiple requests are more likely to coincide with the expiration time and trigger simultaneous cache misses.

5. Event-based cache invalidation:

In systems where cache invalidation is triggered by specific events, such as data updates or changes, a high frequency of events can cause cache stampedes. If multiple events occur simultaneously or in rapid succession, they can lead to concurrent cache misses and subsequent resource regeneration.

6. Caching hotspots:

Certain cache entries or resources might experience higher traffic or popularity compared to others. If a popular cache entry expires or becomes invalidated, the subsequent cache misses can result in a cache stampede, especially if there is no effective mechanism to handle the sudden surge in demand.

It’s important to consider these causes when designing and implementing caching strategies. Employing appropriate cache management techniques, such as intelligent expiration policies, asynchronous caching, and concurrency control mechanisms, can help mitigate the cache stampede problem and ensure the smooth operation of the system.

The Cache Stempede or Dogpile Problem is defined as a situation where the system receives multiple requests for a cached resource simultaneously for which the cache has already expired or has become invalid.

Cache Stampede or Dogpile Problem in System Design is a phenomenon that can occur in systems that rely on caching to improve performance. As a result, the system experiences a sudden surge in demand, often overwhelming the backend resources and causing a performance degradation.