OpenSearch is an open-source search engine that was initially developed by Amazon as a fork of Elasticsearch, a popular enterprise search engine. The two are now competing in the market, with OpenSearch being licensed under the Apache 2.0 license and Elasticsearch under the Server Side Public License (SSPL) and Elastic license. Both offer similar features such as multi-tenant architecture, analytics engine, full-text search, and distributed search capabilities. However, licensing terms have changed for Elasticsearch, requiring users to release source code and APIs necessary for third-party use. OpenSearch is currently licensed under the Apache 2.0 license, while Amazon offers its own cloud-based managed service, Amazon OpenSearch Service, which allows AWS customers to launch scalable clusters and connect data sources to cluster endpoints. The two search engines have diverged in terms of features, with OpenSearch removing telemetry collection functionality and some advanced security features from Elasticsearch. Performance-wise, Elasticsearch is currently faster than OpenSearch, but pricing can vary depending on usage and cloud provider. Ultimately, both solutions are comparable for mainstream use cases, but ChaosSearch provides an alternative with reduced management overhead, high scalability, and lower TCO.