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What Is Cache Hit Rate

Cache hit rate, known also as cache hit ratio, is a measure of the effectiveness of a cache, which is a temporary storage area for frequently accessed data. The cache hit rate is the percentage of requests for data that can be served by the cache, rather than having to be retrieved from the origin server.

For example, if a CDN receives 100 requests for content and 60 of those requests can be served by the cache, the cache hit rate is 60%. A high cache hit rate indicates that the cache is effective at storing and serving frequently accessed data, which can improve the performance and speed of a website.

Cache hit rate is an important metric for CDNs, as it can affect the performance and speed of a website.

Cache hit ratio for CDNs

High cache hit ratio can be an indication that a CDN is well-designed and is able to deliver content efficiently to users. In general, a CDN with a high cache hit ratio will be able to serve more content from its cache, which can improve the performance and speed of a website.

Uploadcare's CDN is designed to provide high cache hit rates for popular content. We use advanced algorithms to manage cache and ensure that your files are served quickly.

What is a cache hit or miss?

Cache Hit

A cache hit occurs when a request for data is satisfied by the cache, rather than having to be retrieved from the origin server. This means that the data is already stored in the cache and can be quickly and efficiently served to the user.

Cache Miss

Cache miss occurs when a request for data cannot be satisfied by the cache, and the data must be retrieved from the origin server. This can be due to the data not being stored in the cache, or because the cache is full and the data has been evicted to make room for newer data. Cache misses can be slower and less efficient than cache hits, as they require data to be retrieved from the origin server.

In general, a high cache hit rate is desirable, as it indicates that the cache is effective at storing and serving frequently accessed data.

A low cache hit rate, on the other hand, may indicate that the cache is not being used effectively, or that the cache is too small to store all the frequently accessed data.

What is a good cache hit rate?

There is no definitive answer to what constitutes a "good" cache hit rate, as it can vary depending on the type and size of the cache, the popularity of the content being served, and other factors. In general, a cache hit rate of 80-95% is considered to be good, but this can vary depending on the specific situation.

It is important to consider other factors, such as the size of the cache and the rate at which data is being added to the cache. A large cache with a high cache hit rate may not be as effective as a smaller cache with a slightly lower hit rate, if the large cache is unable to store all the frequently accessed data. In this case, a smaller cache may be more effective at storing and serving the most popular content.

How is cache hit rate calculated?

This can be simply expressed mathematically as:

Formula of cache hit rate calculation

How can hit rate be improved?

  • Use advanced algorithms to manage the cache: CDNs can use algorithms to predict which content is likely to be requested in the future, and store that content in the cache. This can improve the cache hit rate by ensuring that the most popular content is always available in the cache.
  • Use a distributed cache: A distributed cache is a cache that is spread across multiple servers, which can improve the cache hit rate by allowing more data to be stored in the cache. This can be especially useful for websites with large amounts of data that need to be served quickly and efficiently.
  • Use a larger cache: A larger cache can store more data, which can improve the cache hit rate by allowing more requests to be satisfied by the cache. However, it is important to balance the size of the cache with the rate at which data is being added to the cache, to ensure that the cache is not overfilled.

Overall, there are many factors that can affect the cache hit rate, and the best approach to improving it will depend on the specific situation. Nothing new here huh ;)