Decide if you want to use Azure Cache for Redis

  • 5 minutes

Your sports website has a database behind it that returns data by executing queries. However, performance slows down when the load is high, particularly during large sporting events. In hosted environments, increased resource usage translates into higher costs. Caching data ensures your website performs well and runs economically.

What is caching?

Caching is the act of storing frequently accessed data in memory very close to the application that consumes the data. You can use caching to increase performance and reduce the load on your servers. We use Redis to create an in-memory cache that can provide excellent latency and potentially improve performance.

What is a Redis cache?

Redis (REmote DIctionary Server) cache is an open-source, in-memory key value pair store. It's popular because it's fast and can store and manipulate common data types such as strings, hashes, and sets. It's also considered developer-friendly, as it supports multiple languages such as Python, C, C++, C#, Java, and JavaScript, among others.

What is Azure Cache for Redis?

Azure Cache for Redis is based on the popular open-source Redis cache. It gives you access to a secure, dedicated Redis cache managed by Microsoft. A cache created using Azure Cache for Redis is accessible from any application within Azure. Azure Cache for Redis is typically used to improve the performance of systems that rely heavily on back-end data stores.

Your cached data is located in-memory on an Azure server running the Redis cache as opposed to being loaded from disk by a database. Your cache is also highly scalable. You can alter the size and pricing tier at any time.

What type of data can be stored in the cache?

Redis supports various data types, all oriented around binary safe strings. You can use any binary sequence for a value, from a string like "i-love-rocky-road" to the contents of an image file. An empty string is also a valid value.

  • Binary-safe strings (most common)
  • Lists of strings
  • Unordered sets of strings
  • Hashes
  • Sorted sets of strings
  • Maps of strings

Each data value is associated with a key that can be used to look up the value from the cache. Redis works best with smaller values (100 kB or less), so consider chopping up bigger data into multiple keys. Storing larger values is possible (up to 500 MB), but increases network latency and can cause caching and out-of-memory issues if the cache isn't configured to expire old values.

What is a Redis key?

Redis keys are also binary-safe strings. Here are some guidelines for choosing keys:

  • Avoid long keys: They take up more memory and require longer lookup times because they have to be compared byte-by-byte. If you want to use a binary blob as the key, generate a unique hash and use that as the key instead. The maximum size of a key is 512 MB, but you should never use a key that size.
  • Use keys that can identify the data: For example, sport:football;date:2008-02-02 would be a better key than fb:8-2-2. The former is more readable, and the extra size is negligible. Find the balance between size and readability.
  • Use a convention: A good convention is object:ID, as in sport:football.

How is data stored in a Redis cache?

Data in Redis is stored in nodes and clusters.

Nodes are a space in Redis where your data is stored.

Clusters are sets of three or more nodes across which your dataset is split. Clusters are useful because your operations continue if a node fails or is unable to communicate to the rest of the cluster.

What are Redis caching architectures?

Redis caching architecture is how we distribute our data in the cache. Redis distributes data in three major ways:

  1. Single node
  2. Multiple node
  3. Clustered

Redis caching architectures are split across Azure by tiers:

Basic cache

A basic cache provides you with a single node Redis cache. The complete dataset is stored in a single node. This tier is ideal for development, testing, and noncritical workloads.

Standard cache

The standard cache creates multiple node architectures. Redis replicates a cache in a two-node primary/secondary configuration. Azure manages the replication between the two nodes and creates a production-ready cache with primary/secondary replication.

Premium tier

The premium tier includes the features of the standard tier, but adds the ability to persist data, take snapshots, and back up data. With this tier, you can create a Redis cluster that shares data across multiple Redis nodes to increase available memory. The premium tier also supports an Azure Virtual Network to give you complete control over your connections, subnets, IP addressing, and network isolation. This tier also includes geo-replication, so you can ensure your data is close to the app that's consuming it.

Summary

A database is great for storing large amounts of data, but there's an inherent latency when looking up data. You send a query. The server interprets the query, looks up the data, and returns it. Servers also have capacity limits for handling requests. If too many requests are made, data retrieval is likely to slow down. Caching stores frequently requested data in memory that can be returned faster than querying a database, which should lower latency and increase performance. Azure Cache for Redis gives you access to a secure, dedicated, and scalable Redis cache, hosted in Azure and managed by Microsoft.