Redis vs KeyDB

Redis and KeyDB are both powerful in-memory database systems known for their speed and efficiency in data processing. Despite their similarities, there are significant differences between the two technologies.

Redis

• Origin and Distribution: Redis (Remote Dictionary Server) was originally developed by Salvatore Sanfilippo and is widely used in the industry as a powerful and flexible in-memory database for caching, session management, pub/sub, and more scenarios.
• Licensing: Redis is released under the BSD license, which is very permissive and imposes few restrictions on use and distribution. Over time, Redis has introduced a dual licensing model, especially for its advanced modules and enterprise features.
• Architecture and Performance: Redis uses a single-threaded architecture known for its simplicity and high performance. It supports various data structures like strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, and geospatial indexes with radius queries.
• Extensibility and Modules: Redis offers a module system that allows the functionality of the database to be extended through third-party or custom modules.
• Community and Support: As one of the most popular open-source projects, Redis has a large and active community. There is extensive documentation, tutorials, and third-party tools available.

KeyDB

• Origin and Distribution: KeyDB is a fork of Redis, distinguished by its multithreading capability. The main goal of KeyDB is to enhance Redis’s performance through multithreading to achieve higher throughput and better utilization of modern multi-core CPUs.
• Licensing: KeyDB is also released under an open-source license, with the specific licensing model depending on the version and specific components.
• Architecture and Performance: Unlike Redis, KeyDB uses a multithreading architecture that allows efficient use of multiple processor cores to achieve higher throughput rates and better scalability, especially for workloads involving many connections and commands.
• Compatibility with Redis: KeyDB strives to remain compatible with Redis, meaning applications written for Redis can often work with KeyDB without changes. KeyDB supports the same protocols and data structures as Redis.
• Extensions and Differences: In addition to multithreading, KeyDB adds its own extensions and improvements that go beyond the core functions of Redis, such as improved replication and additional commands.

Conclusion

Although Redis and KeyDB are similar in many aspects, they mainly differ in their internal architecture and performance optimization. Redis is known for its stability and large user community, while KeyDB is positioned as a more powerful alternative through the use of multithreading and additional optimizations. The choice between Redis and KeyDB ultimately depends on the specific requirements of the project, the preferred architecture, and performance expectations.

Redis: Transition to RSALv2

In March 2024, Redis announced a significant change to its licensing model. The core technology of Redis, known for its in-memory database systems, will transition from the previous BSD 3-Clause License to a dual licensing model. This model includes the Redis Source Available License Version 2 (RSALv2) and the Server Side Public License Version 1 (SSPLv1), starting with Redis Version 7.4 and for all future versions【5†source】.

RSALv2 is described as a permissive, non-copyleft license that allows the use, reproduction, distribution, availability, and creation of derivative works of the software code, provided the software is not commercialized or offered as a managed service. Additionally, no license, copyright, or other notices may be removed or obscured Source. In contrast, the SSPL is based on the GNU Affero General Public License (AGPL) with a modified clause requiring any modified or unmodified software offered as a service to be made publicly available under the SSPL Source.

For the developer community and existing Redis Enterprise customers, practically nothing changes; the Redis developer community can continue to benefit from permissive licensing, and all Redis client libraries remain open-source licensed. Redis emphasizes that the new licensing model represents the best compromise to make the Redis source code widely available, support the developer community with minimal restrictions, and simultaneously protect their investments in rich, free software and enterprise products.

In addition to the changes in the licensing model, Redis has announced the discontinuation of Redis Stack once Redis 8 becomes available, as Redis 8 will integrate new data types and processing engines, previously licensed under RSALv2 or SSPLv1, directly into Redis itself.

This change reflects Redis’s commitment to providing all developers with access to the best available technology while enabling simple and consistent packaging and release of additional data types and more in a way that aligns with Redis’s original vision.