In computing, the term caching refers to storing frequently accessed data temporarily in a faster memory or storage. This process improves performance by reducing the time and resources needed to fetch data from its main source. When data is cached, users can access the data faster than if it needed to come from slower storage, such as a disk or over the network.
What Is Caching?
Caching is the practice of storing data in a temporary location, or cache, so it can be retrieved quickly. This allows people to enjoy fast access to copies of files and other data without having to download the data each time they need it.
How Does Caching Work?
When a program needs to access particular data, it first checks the cache memory to see if it’s available. If the program finds the data there, that’s called a cache hit, and it retrieves the data quickly. If the data is not there, that’s called a cache miss, and the program then fetches the data from the main storage, such as a file or a web page, and adds it in the cache for future use.
Web browsers, for example, cache information such as images and scripts. When you revisit a website, the browser quickly loads the cached data instead of downloading it again, resulting in faster page load times.
Cache has limited storage space. If there is no room for the new data, the program uses cache replacement policy to remove older data from the cache to make room for the new data. For example, least recently accessed or least frequently used data may be removed. In some cases, cached data may need to be invalidated if it’s no longer relevant to ensure cache accuracy.
Caching Benefits
Caching comes with a number of other upsides:
- Faster Data Access: Caching can significantly reduce response time to access frequently requested data.
- Improved Performance: Lower data access latency improves overall computing performance by allowing applications to execute tasks quickly.
- Resource Usage and Scalability: By reducing the load on the main data source, caching helps reduce resource usage, including lower CPU usage, disk I/O and network traffic. This makes the system more efficient and scalable.
- Offline Access: In some cases, caching allows users to access data or content offline, such as cached web page elements. This improves the user experience for those with limited connectivity.
- Cost Savings: Due to lower resource usage and higher scalability, caching saves the cost of maintaining the main data source.
Types of Caching
There are several different types of cache used in computer systems. Here are some examples:
Browser Cache
Web browsers store images, scripts and style sheets locally. When a user returns to a web page they’ve previously browsed, the website can quickly retrieve content stored in browser cache and rearrange it without having to load everything all over again. This results in faster load times and a smoother online user experience.
Disk Cache
This buffer cache is used in hard drives and solid-state drives to temporarily store recently accessed data from the disk while also improving read and write performance.
DNS Cache
Domain Name System, or DNS, servers maintain cache of domain name to IP addresses mapping. For example, if the domain name is Dropbox.com, it’s translated to an IP address like 162.125.1.18. This mapping from domainname<>ipaddress gets stored in DNS cache. When the next hit comes, the program won’t need to go to the main server to find the IP address for a domain.
Application Cache
Some applications, such as database systems and web servers, implement custom caching to store frequently accessed data or query results to improve application responsiveness.
CPU Cache
Caching was initially invented to speed up code and data access by the CPU, or computer processing unit. The L1 cache, located on the CPU chip, is useful for frequently used code instructions and data to stop programs constantly fetching from the slower memory. The larger L2 cache serves as secondary storage, and is located closer to the CPU than the main memory. Finally, an even larger L3 cache can be shared among multiple CPU cores for frequently accessed data across those cores.
Caching Use Cases
Besides the types of caching described above, there are many other use cases that demonstrate the benefits of caching.
CDNs
Content Delivery Networks, or CDNs, cache static content such as images, videos and installation files across distributed edge servers located closer to users. This process reduces latency, improves speed and saves on costs for data access across geographically distributed audiences.
Session Caching
Session caching stores session data, including user authentication tokens during user sessions. This speeds up user interactions in web applications.
Operating Systems
Operating systems and file systems use caching to store recently accessed files or file metadata. This accelerates file read/write performance and reduces disk access to improve speed.
Search Engines
Search engines cache search results and indexed web pages to deliver faster search query responses.
Caching Best Practices
Caching plays a significant role in optimizing system performance and improving user experience. The following suggestions will help you create an efficient caching strategy.
1. Develop a Clear Goal
Establish goals that caching needs to accomplish, whether it be faster web page loading or an improved search engine experience. Take into account multiple audience segments as well to design a caching strategy that benefits the most users possible.
2. Select a Cache Storage
Choose a cache storage type that fulfills your goals and user needs. Depending on the application, in-memory caches like Redis or Memcached may work best. Otherwise, it might make more sense to use disk-based or distributed caches like Hazelcast or Apache Ignite.
3. Prepare Your Data
Identify the data to cache in your application. Data that’s frequently accessed and does not change often is usually a good choice. Consider pre-loading this data into the cache on startup or during low-traffic periods.
4. Develop Caching Strategies
Use cache invalidation strategy to keep the cached data accurate. For instance, you might use time or event-based invalidation to invalidate state data. Implement cache-backing strategies, such as read-through and write-through, to ensure data consistency between the cache and main data source. Design cache keys to ensure efficient data retrieval and utilization. When applicable, implement tiered or layered cache to further optimize latency and performance.
5. Protect Your Cache
Take steps to secure cached data. Set up end-to-end encryption, strict access controls and other safeguards to defend against cyber attacks. To limit opportunities for hackers to strike, implement error handling and fallback to handle failures and timeouts gracefully.
6. Evaluate Cache Performance
Monitor cache performance including usage, hit rates and eviction rates. Adjust your strategy accordingly based on the results. Pick a shorter cache expiration period for volatile data and a longer expiration period for relatively static data. Stay aware of this timeline while observing cache to make sure it’s followed.
Frequently Asked Questions
Is deleting cookies the same as clearing the cache?
No, deleting cookies is not the same as clearing the cache. Cookies store data about a user, such as website visits and preferences. Deleting cookies will result in a user’s information being erased, so a user will need to log in to sites and select their preferences again. Cache stores data like web pages and images, and is used to speed up loading times. Clearing the cache will remove temporary copies of data and files. This means a user will see a brand-new version of a web page instead of a previously saved version.
What is an example of a cache?
A common example of a cache is a browser cache. This cache stores information dowloaded from web pages, including videos, images and HTML and CSS code.
