1. A system, comprising: one or more computers configured to implement an index-based query system, wherein the index-based query system comprises: an index generation module configured to generate a plurality of forward indices, wherein individual forward indices of the plurality of forward indices comprise a plurality of pointers to a plurality of locations in a storage subsystem, wherein the plurality of locations in the storage subsystem store a plurality of modifications to a respective document of a plurality of documents, and wherein the individual forward indices correspond to different respective documents of the plurality of documents; a metadata generation module configured to generate metadata describing the forward indices of the plurality of forward indices, respectively, wherein the metadata comprises respective identifiers of the plurality of documents and a plurality of time ranges, wherein the metadata indicates which of the plurality of forward indices for a particular document identifier includes updates for a particular time range, and wherein different indices of the plurality of forward indices cover different time ranges; and a query module configured to: load the metadata; receive a query request after loading the metadata, wherein the query request comprises an identifier of a particular document of the plurality of documents and a specified time range; determine a requested subset of the forward indices, wherein to determine the requested subset the query module is configured to search the metadata for the identifier of the particular document in the specified time range; retrieve, from the requested subset of the forward indices, a requested subset of the plurality of pointers corresponding to one or more modifications to the particular document in the specified time range; and retrieve, from the storage subsystem, the one or more modifications to the particular document in the specified time range using the requested subset of the plurality of pointers.