Abstract: We describe data structures and an update strategy for e practical implementation of inverted indexes. The context of our discussion is the construction of a dedicated index engine for a distributed full-text information retrieval system but the results have wider applications. Retrieval operations require a single disk access per query term. The online update strategy guarantees the consistency of on-disk data structures. Index compression integrates smoothly.

Keywords: NNquery, Inverted Index, Lucene, Elastic Search.