Lucene

Percona server is an opensource, fully compatible, enhanced drop-in replacement for MySQL, providing superior performance, scalability, and instrumentation.

Amazon Aurora is a relational database service developed and offered by Amazon Web Services.

Solr is an open-source enterprise-search platform, written in Java.

MariaDB is an open-source relational database management system that is a fork of MySQL. It's designed to be a drop-in replacement for MySQL with more features, new storage engines, and improved performance. MariaDB offers features like advanced clustering with Galera Cluster, more storage engines, and better performance optimizations. Its commitment to remaining open-source and its compatibility with MySQL make it an attractive option for organizations looking for a powerful, community-driven database solution.

Redis is an open-source, in-memory data structure store that can be used as a database, cache, message broker, and queue. It supports various data structures such as strings, hashes, lists, sets, and more. Redis is known for its high performance, flexibility, and support for atomic operations. Its ability to persist data to disk and replicate data across multiple servers makes it suitable for a wide range of use cases, from simple caching to complex real-time applications. Redis's speed and versatility make it popular among developers for building high-performance, scalable applications.