9. A system that includes a processor coupled to computer-storage media and that deems a document to be relevant to a search query, the system comprising: a search engine having a search-query receiver that receives the search query, which includes a search term, wherein the search engine includes a plurality of computing devices that each process a respective set of documents, wherein each computing device of the plurality of computing devices comprises a term-index lookup table, a term index, a per-document-index lookup table, and a per-document index, wherein the term index includes a plurality of term postings, each term posting including a respective term and a document identifier of each document deemed relevant to the respective term; and wherein each term posting omits information indicating locations at which the respective term is found in each document; a matcher that determines that one or more documents are relevant to the search term by reviewing the plurality of term postings and finding a match between the search term and at least one of the respective terms; and a ranker that determines a search-result rank of the one or more documents determined to be relevant by using the document identifier of each document to access a per-document index lookup table, which maps each document identifier to document-ranking information in the per-document index, and by ranking the one or more documents according to the document-ranking information retrieved from the per-document index for each document, wherein the per-document index organizes the document-ranking information relevant to a document into a per-document index header, a term-to-ID mapping, and a document-specific term index; wherein the term-to-ID mapping maps the search term to a unique identifier that identifies the search term in the document specific term index; wherein the document-specific term index stores position information that describes one or more positions of the search term in the document and that is used to determine the search-result rank of the document; and wherein search results that are served include a listing of the one or more documents presented consistent with the search-result rank.
9. A system that includes a processor coupled to computer-storage media and that deems a document to be relevant to a search query, the system comprising: a search engine having a search-query receiver that receives the search query, which includes a search term, wherein the search engine includes a plurality of computing devices that each process a respective set of documents, wherein each computing device of the plurality of computing devices comprises a term-index lookup table, a term index, a per-document-index lookup table, and a per-document index, wherein the term index includes a plurality of term postings, each term posting including a respective term and a document identifier of each document deemed relevant to the respective term; and wherein each term posting omits information indicating locations at which the respective term is found in each document; a matcher that determines that one or more documents are relevant to the search term by reviewing the plurality of term postings and finding a match between the search term and at least one of the respective terms; and a ranker that determines a search-result rank of the one or more documents determined to be relevant by using the document identifier of each document to access a per-document index lookup table, which maps each document identifier to document-ranking information in the per-document index, and by ranking the one or more documents according to the document-ranking information retrieved from the per-document index for each document, wherein the per-document index organizes the document-ranking information relevant to a document into a per-document index header, a term-to-ID mapping, and a document-specific term index; wherein the term-to-ID mapping maps the search term to a unique identifier that identifies the search term in the document specific term index; wherein the document-specific term index stores position information that describes one or more positions of the search term in the document and that is used to determine the search-result rank of the document; and wherein search results that are served include a listing of the one or more documents presented consistent with the search-result rank. 12. The system of claim 9 , wherein the per document-index lookup table maps the document identifier to the document-ranking information in a solid-state drive.