Let’s discuss what caching is, why it is important, and the best open-source caching you can install on your server.

Caching: A Closer Look

The process of storing copies of data in a temporary storage location is known as caching or content caching. This temporary storage location is named Cache. The purpose of caching is to easily retrieve the data from the original storage. Caching enables the efficient reuse of data that has already been retrieved or computed. Keep reading to explore the top 10 open-source Linux caching tools.

1. Redis

Remote Dictionary Server, popularly known as Redis, works as a caching engine that supports many of the data structures like lists, sets, sorted sets, bitmaps, hashes, etc. Redis is well-known for its exceptional speed, which is primarily due to its approach of storing and delivering all data from memory instead of using disk storage. It is a free, open-source, high-performance, and flexible distributed in-memory computing system. Redis stands out in some situations requiring specific data structures and automatic operations such as string appending and list pushing.

Key Features of Redis:

• Master-slave replication, high availability via Redis Sentinel, and horizontal scaling with Redis Cluster, and data partitioning.
• Supports transactions, Lua scripting, various persistence options, and client-server encryption.
• While optimized for in-memory datasets, it can complement on-disk databases like MySQL and PostgreSQL for mixed data management.

2. Memcached

Memcached is a free, open-source distributed memory object caching system that is designed to increase the speed of dynamic web applications by caching small data chunks like database results, API responses, or rendered pages. It operates as an in-memory key-value store and supports Unix-like systems (including Linux and OS X) as well as Microsoft Windows. Primarily, Memcached uses a Least Recently Used (LRU) cache to reduce the load on-disk databases and acts as a short-term memory for applications.

Key features of Memcached:

• It supports strings as its sole data type and employs a client-server architecture, where clients handle server selection and connection management.
• While it supports clustering by adding more servers to increase memory, Memcached servers are independent and do not support replication.
• Provides an API compatible with popular programming languages.
• Security features include experimental support for authentication and TLS encryption as of version 1.5.13. This makes Memcached a simple yet powerful tool for caching and improving web application performance.

3. Apache Ignite

Apache Ignite is the third tool on the list. Like others, Apache Ignite is a free, open-source, horizontally scalable distributed in-memory key-value store, cache, and multi-model database system. It runs on UNIX-like systems and Windows, featuring multi-tier storage, complete SQL support, and ACID transactions at the key-value API level across multiple cluster nodes.

Key features of Apache Ignite:

• Supports co-located processing and machine learning and integrates effortlessly with third-party databases like MySQL and PostgreSQL.
• While it functions as an SQL data store, it is not a full SQL database and lacks traditional constraints like foreign keys.
• Security features include authentication and SSL socket communication.
• Uses cases including caching, workload acceleration, real-time data processing, and analytics.

4. Couchbase Server

Couchbase Server is also an open-source, distributed NoSQL document-oriented database designed for high performance and scalability. It stores data in a key-value format and supports Linux, Windows, and Mac OS X. Couchbase uses N1QL, a powerful query language for advanced querying and indexing, that enables sub-millisecond data operations.

Key features of Couchbase:

• Fast key-value store with managed cache, purpose-built indexers, a robust query engine, and multidimensional scaling.
• It supports big data and SQL integration, full-stack security, and high availability.
• Couchbase’s cluster manager coordinates node activities, which allow simple node addition, removal, or replacement without downtime.
• It also offers data replication within clusters and across data centers.

Security is ensured through TLS, authentication mechanisms, role-based access control, auditing, and logging. Couchbase is ideal for low-latency data management in large-scale web, mobile, and IoT applications that support use cases like full-text search, parallel query processing, and document management.

5. Hazelcast IMDG

Hazelcast IMDG (In-Memory Data Grid) is an open-source, lightweight, and fast middleware that provides scalable, distributed in-memory computing. It operates on platforms with Java, including Linux, Windows, and Mac OS X. It includes APIs for accessing cluster CPUs for maximum processing speed and offers distributed implementations of Java interfaces such as Map, Queue, ExecutorService, Lock, and JCache.

However, advanced security features are primarily available in the enterprise version. Hazelcast is ideal for applications requiring high performance, scalability, and robust security.

Key features of Hazelcast:

• Hazelcast supports various flexible data structures like Map, Set, List, MultiMap, RingBuffer, and HyperLogLog.
• It uses a peer-to-peer architecture for simple scalability and cluster setup, offering tools for statistics, monitoring, and management via the JMX protocol.
• Hazelcast ensures redundancy by backing up each data entry for multiple members and balancing data and backups automatically when new instances are added.
• Security features include cluster member and client authentication, access control, socket-level communication encryption, and SSL/TLS support.

6. Mcrouter

Mcrouter is a free, open-source Memcached protocol router developed by Facebook for scaling Memcached deployments. It supports the Memcached ASCII protocol, flexible routing, multi-cluster setups, multi-level caches, connection pooling, and multiple hashing schemes.

Key features of Mcrouter:

• Include prefix routing, replicated pools, traffic shadowing, online reconfiguration, and automatic failover with destination health monitoring.
• Additional functionalities are cold cache warm-up, extensive stats and debug commands, reliable delete stream quality, handling of large values, broadcast operations, IPv6, and SSL support. Mcrouter is crucial to Facebook and Instagram, which manage nearly 5 billion requests per second at peak.

7. Varnish Cache

Varnish Cache is an open-source web application accelerator that improves web server performance by caching content in memory. Running on Linux, FreeBSD, and Solaris, it sits between web clients and origin servers like NGINX or Apache. Varnish forwards client requests to the web server, caches the responses, and serves cached content to clients, boosting response times and reducing server load.

Key features of Varnish:

• It features Varnish Configuration Language (VCL) for request handling and supports extensions called VMODS.
• Security features include logging, request inspection, and throttling, though SSL/TLS requires an external proxy.
• Varnish can also function as a web application firewall, load balancer, and more.

8. NGINX

NGINX is an open-source, high-performance server solution widely used for web infrastructure. It functions as an HTTP server, a reverse proxy, a mail proxy, and a generic TCP/UDP proxy.

Key features of NGINX:

• Offers basic caching capabilities, including storing content in a persistent disk cache and delivering stale content if fresh content is unavailable.
• Its robust security features include SSL termination, HTTP basic authentication, JWT authentication, and access restriction by geography.

Commonly, NGINX is deployed as a reverse proxy, load balancer, SSL terminator, application accelerator, content cache, API gateway, and for streaming media, enhancing performance and security across application stacks.

To Sum Up

Caching is crucial for improving the performance and responsiveness of websites and applications by storing copies of frequently accessed data. This reduces the need for repeated database queries or computations, speeding up load times and enhancing user experience. Effective caching reduces server load, bandwidth usage, and costs, while improving scalability. Proper cache management ensures users always receive up-to-date information. Implementing a robust caching strategy is essential for fast, efficient, and user-friendly digital experiences.