Efficient duplicate prevention in event-based data within Elasticsearch involves generating unique identifiers for documents before indexing to avoid duplication, which can lead to incorrect analyses and search errors. Two primary methods for creating these identifiers are the use of Universally Unique Identifiers (UUIDs) and hash-based identifiers, each with distinct advantages and potential drawbacks in terms of uniqueness and indexing performance. UUIDs, generated at the event's origin, offer a high level of uniqueness but may not be feasible in all systems, while hash-based identifiers depend on the event content and can be assigned later in the processing pipeline. Elasticsearch's internal identifier generation optimizes indexing performance, but when external identifiers are used, performance can be impacted due to required update checks. To balance performance with duplicate prevention, strategies such as timestamp-prefixing and utilizing the rollover and split index APIs can be employed, although these have implications for managing index sizes and maintaining the link between event timestamps and their indices. It is recommended to benchmark and tailor these approaches to specific use cases to ensure optimal performance and accuracy in event data management.