In this technology-driven world, where we are always on our Internet-connected devices for carrying out our professional as well personal work, there is hardly anyone who has not come across the term “cache”. The information that is being disseminated here will aid in better understanding the concept of caching.
Caching
Caching refers to the process of not only storing but also recalling saved data. To explain a cache in the simplest way, it is a storage location that is reserved for collecting data that is of temporary nature to enable fast loading of browsers, websites and apps. Regardless of the type of Internet-connected device (phone, personal computer, tablet) that you use, there will be some type of cache in it. The same is true for your web browser or application. A cache can be understood as a data storage layer that functions at high-speed and serves the purpose of storing a subset of data which is of transient nature. This enables future requests for data to be served faster than the speed at which that could have happened while accessing the primary storage location of the data. In this way caching enables the effective reuse of data that had been retrieved previously and makes it easy to swiftly retrieve data, ensuring that devices run faster.
Fast access hardware, such as Random-access Memory (RAM), usually stores the data in a cache. The main function that a cache serves has to do with enhancing data retrieval performance. This is attained by reducing the requirement to access the underlying slower storage layer. A cache trades off capacity for speed. It typically stores a subset of data temporarily, which is in stark contrast to databases whose data is generally durable as well as complete. A cache functions in a way which is similar to a memory bank. This renders it easy to access data locally rather than downloading it time and again, when a website is visited or an app is opened.
Data processed by an app is taken by the cache and stored for later use. Websites and their underlying technology use cache a lot. The following elements are often included in a cache-
The Caching Software – The process is run by the caching software, which shuttles it between the different elements.
Random-access Memory (RAM) and In-Memory Engines – These are meant for storing the data passed by the caching technology.
The aforementioned elements need to be not only collaborative but also of high quality. That is because a RAM that performs slowly will not be capable enough to recall data quickly enough for its efficient use by the software. Let us discuss, in brief, RAM and In-Memory engines in this context. The high request rates or IOPS (Input/Output Operations Per Second) that are supported by RAM and In-Memory engines impact caching results, ensuring enhanced data retrieval performance along with diminished cost at scale. There will be the requirement of additional resources for supporting the same scale with databases that are traditional and hardware that are disk-based. Moreover, these additional resources not only increase cost but also fail to attain the low latency performance that is provided by an In-Memory cache. Workloads that are compute-intensive and which manipulate data sets, such as high-performance computing simulations and recommendation engines, benefit greatly from an In-memory data layer acting as a cache.
To digress, every website is made accessible through the service of web hosting which is delivered through various web hosting plans by website hosting companies. A web hosting company is also referred to as a web host. The data of websites are stored on web servers and are processed on it and then delivered to browsers for rendering websites accessible. Websites that deliver an outstanding quality of service, wherein pages load quickly and websites are always up and running are often referred to as the “Best Cloud Hosting Company”, the “Best Windows Hosting Company”, etc. In the context of websites and web applications, a cache is a necessary element, given the length of file sizes. A cache contributes significantly to fast site loads and it is the caching software of the website’s server that is at the core of this visible result.
The following different technologies are involved with regard to caching, wherein servers are used in some capacity-
Apps – These have a cache for storing data that is frequently used.
Browsers – Regular requests are stored in the cache of a browser cache to ensure faster loading for the next time.
Devices – A device’s browsers and apps often use its storage and RAM for caching data.
Servers – Server data is stored on and recalled from a cache to attain faster execution and processing.
DNS (Domain Name Server) Caching – It refers to an application that is focussed on caching. Smooth operation is ensured by a DNS cache.
The application of caches and their leveraging is possible throughout various layers of technology, such as web applications, databases, Operating Systems and Networking layers which include CDN (Content Deliver Networks) and DNS. Caching can be successfully used for significantly reducing latency and improving IOPS for a large number of application workloads that are read-heavy. These include gaming, Q&A portals, media sharing, social networking, etc. Cached information can take the form of computationally intensive calculations, API requests/responses, results of database queries as well as web artifacts such as HTML, JavaScript, and image files.
With regard to design patterns, a dedicated caching layer results in systems and applications running independently from the cache to have their own lifecycles without affecting the cache. The cache functions as a central layer which is accessible to disparate systems. Its relevance increases in a system where it is possible to dynamically scale in and out application nodes. When the cache resides on the same node as those systems and applications that are utilizing it, then scaling might affect the cache’s integrity. The local application, which is consuming the data, is the only one to benefit when local caches are used. Data usually span multiple cache servers in a distributed caching environment and get stored in a central location for the benefit of all those that would be consuming the data.
Caching Best Practices
The best practices with regard to caching need to be taken care of. It is essential to understand the validity of the data that is being cached while implementing a cache layer. A high hit rate is caused by a successful cache. This indicates that the data was present when it was fetched. In the event that the fetched data was not there in the cache, then a cache miss is said to have occurred. Certain controls can be applied accordingly to expire the data. Such a control is Time to Live (TTL).
Another important factor that needs to be considered has to do with whether or not the cache environment needs to be Highly Available that is satisfied by In-Memory engines. Certain cases require the use of an In-Memory layer as a standalone data storage layer which works in contrast to the caching of data from a primary location. Such a situation calls for defining an appropriate Recovery Time Objective (RTO) and Recovery Point Objective (RPO) on the data in the In-Memory engine for assessing its suitability. RTO indicates the time that is taken to recover from an outage, whereas RPO refers to the last point or transaction captured in the recovery. Most of the RTO and RPO requirements can be catered to successfully by the design strategies and characteristics of different In-Memory engines.
Caching Benefits
Before concluding, let us touch on some of the main benefits of caching. These are being mentioned below, in no particular order-
Increase Read Throughput (IOPS) – Apart from lowering latency, caching results in much higher request rates (IOPS) relative to a comparable disk-based database. Thousands of requests can be served in a second by a single instance that is used as a distributed side-cache.
Enhanced Application Performance – Reading data from cache is extremely fast. An application’s overall performance gets boosted by the significantly fast speed at which data is accessed.
Reduced Load on the Backend – Caching is able to reduce the load on database by redirecting a huge part of the read load from the backend database to the in-memory layer. Additionally, it ensures protection against slower performance under load, as well as against crash during times of spikes.
Reduced Database Cost – Innumerable IOPS are provided by a single cache instance. This is capable of replacing a significant number of database instances, which helps to reduce the total cost.
Predictability of Performance – When the load on the database increases, the result is visible in the form of higher latencies to get data. Due to this the overall performance of the application becomes unpredictable. This issue can be mitigated by using a high throughput in-memory cache.
Elimination of Database Hotspots – Hotspots in a database might require overprovisioning of database resources. This will depend on the throughput requirements for the data that are used the most frequently. The need for overprovisioning is mitigated by storing common keys in an in-memory cache. At the same time, it delivers performance that is fast and predictable for data that gets accessed most frequently.
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