Example of Cache Stampede or Dogpile Problem

To demonstrate the cache stampede problem, let’s look at a straightforward example:

Scenario:

• Consider that you have a website application that shows the current weather in various cities, in which you put the weather data into caching to enhance performance, such that each response is cached for a specific amount of time after the weather data is fetched from a distant API.

Arrival of multiple requests:

• Suppose the cached data of a particular city has expired just now. Now, let us imagine that a large number of user requests arrive asking for the weather of that particular city immediately after its expiration.
• Since the data is no longer present in the cache, these requests will then result in cache misses.

How Cache stampede problem comes into picture?

• Now each of these user requests will concurrently try to fetch the weather data from the remote API because they all found the cache to be empty.
• This sudden surge in requests overwhelms the backend resources, causing increased response times, potential service degradation, and additional load on the API server.
• This situation is known as cache stampede.

How does Cache Stampede affect the System in this scenario?

• The cache stampede problem can be particularly impactful when the backend resource or API is slow or resource-intensive. It leads to redundant work being performed, as multiple requests attempt to retrieve the same data simultaneously, instead of leveraging the benefits of caching.

What can be done in this Cache Stampede scenario?

• To mitigate this problem, the following mentioned strategies can be applied:
  • implement cache population techniques,
  • cache locks, or
  • asynchronous caching mechanisms
• You can implement any of the above strategies to handle cache misses more effectively and reduce the impact of simultaneous requests on the backend resources.

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.