Elasticsearch 5.0.0-alpha2, based on Lucene 6.0.0, is a pre-release version designed for testing and feedback rather than production deployment, with indices created in this version being incompatible with the final 5.0.0 GA release. This release, building on the previous alpha1 version, introduces several new features and improvements such as faster indexing and range queries due to the use of dimensional point fields, the replacement of the percolate API with a percolate query for enhanced search functionality, and the implementation of stored scripts/templates to simplify index recovery. It also introduces safety measures, including checks for JVM heap size and virtual memory access, alongside a new circuit breaker to manage the size of all in-flight requests, preventing system overloads. Migration tools like the Elasticsearch Migration Helper are available to assist users in transitioning from Elasticsearch 2.3.x to 5.0, offering functionalities such as cluster checkups, reindexing of old indices, and deprecation logging.