The article explores Elasticsearch from a foundational perspective, gradually moving from basic internal structures to user-facing functionalities. It explains the importance of understanding the mechanics behind Elasticsearch, Lucene, and search engines to optimize their capabilities. Focusing on the inverted index as a core data structure, the article describes how it influences search and indexing efficiency by transforming problems into string-prefix issues. It elaborates on techniques like text processing, index segment creation, and caching to enhance search performance. The article also covers how indexing changes are handled, noting that Lucene indexes are immutable, and updates require deletions and reinsertions. Elasticsearch's architecture is detailed, highlighting its organization into shards and replicas, with a discussion on the implications of this structure for scaling and search customization. The piece underscores the absence of transactions in Elasticsearch, emphasizing its prioritization of speed and efficiency, and sets the stage for a subsequent analysis of Elasticsearch's distributed search capabilities.