Redis
Redis is an in-memory key-value database introduced in 2009 by Salvatore Sanfilippo to solve scalability issues at his startup LLOOGG. It delivers low-latency operations by holding all data in memory and using the fork system call to enable concurrent client service and disk persistence. It supports two persistence methods—RDB snapshotting and AOF journaling—with journaling introduced in version 1.1 and considered safer. Default configuration limits data loss to a few seconds upon full system failure. Redis supports master-replica replication with hierarchical trees and introduced clustering in April 2015 with version 3.0. It grew into one of the world’s most popular databases for caching, message brokering, and primary storage. In December 2024, Sanfilippo returned to Redis and implemented the Vector Set data structure for vector similarity search.