17. A system for incrementally updating a multi-user document index distributed over a plurality of index servers, the system comprising: storage media; one or more processors; and instructions stored in the storage media and configured for execution by the one or more processors, the instructions configured for: generating an index mutation comprising one or more tokens, wherein the one or more tokens are based at least in part on identified differences between a new version of a document and a previous version of the document; appending the index mutation and a version indicator to a log; reading the version indicator associated with the index mutation from the log and comparing the associated version indicator to a value associated with an index of the document, the index of the document stored at an index server of the plurality of index servers; and wherein the value associated with the index of the document stored at the index server represents a latest-updated version of the index; based at least in part on the reading and the comparing, providing the one or more tokens of the index mutation from the log to the index server; and wherein the providing the one or more tokens to the index server causes the index server to use the one or more tokens to update the index of the document stored at the index server.
17. A system for incrementally updating a multi-user document index distributed over a plurality of index servers, the system comprising: storage media; one or more processors; and instructions stored in the storage media and configured for execution by the one or more processors, the instructions configured for: generating an index mutation comprising one or more tokens, wherein the one or more tokens are based at least in part on identified differences between a new version of a document and a previous version of the document; appending the index mutation and a version indicator to a log; reading the version indicator associated with the index mutation from the log and comparing the associated version indicator to a value associated with an index of the document, the index of the document stored at an index server of the plurality of index servers; and wherein the value associated with the index of the document stored at the index server represents a latest-updated version of the index; based at least in part on the reading and the comparing, providing the one or more tokens of the index mutation from the log to the index server; and wherein the providing the one or more tokens to the index server causes the index server to use the one or more tokens to update the index of the document stored at the index server. 18. The system of claim 17 , wherein at least one of the one or more tokens is identified in the new version of the document but not the previous version of the document.