A system and method for providing fine-grained access control in a search engine. Access control predicates associated with a search query, including fixed-width and/or variable-width tokens, are received from the search engine, and are formatted in a machine-readable binary format to generate a single byte array. A pre-sorted memory index structure associated with the single byte array is generated, by sorting the access control predicates according to their token width. The pre-sorted memory index structure is merge joined with an uninverted terms index that includes a sorted list of all terms in a field associated with the search query, and a document index mapping each document identifier (ID) to a term ordinal for a specific field.