Elasticsearch 5.x introduces ten new "bootstrap checks" that run during startup to identify configuration issues that could lead to significant failures under heavy use, particularly when the system is bound to a non-local IP address. These checks, designed to be minor annoyances, include a test for the inappropriate use of the "serial" garbage collector, which can cause nodes to temporarily leave and rejoin the cluster, and a check for low file descriptor limits, which can lead to failures in shard allocation. While the checks initially issue warnings, the Elasticsearch team emphasizes the importance of addressing these configurations to ensure stability and security, transitioning them to errors to compel users to fix the issues before deployment. This approach aims to prevent data loss and system instability in production environments by ensuring that "real" installations meet necessary configuration standards, particularly when setup involves non-local IP addresses indicative of production use.