MariaDB is the more common of the two in our index: it runs on 981 websites against 26 for Redis. Counts come from real scans of each site's home page, not vendor claims, and cover the sites in TechLookup's index rather than the whole web.
MariaDB is an open-source relational database management system compatible with MySQL.
Redis is an in-memory data structure project implementing a distributed, in-memory key–value database with optional durability. Redis supports different kinds of abstract data structures, such as strings, lists, maps, sets, sorted sets, HyperLogLogs, bitmaps, streams, and spatial indexes.
Within the databases sites we have indexed, MariaDB holds 2.4% and Redis 0.1%.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.