19. The computing system of claim 12 , wherein the service request comprises a separate service request for each of the plurality of web pages.
12. A computing system comprising: a data storage system storing: an index comprising a plurality of index entries, the index entries partitioned among a plurality of index partitions, each index partition in the plurality of index partitions associated with at least one website in a plurality of websites; a plurality of external data sets, each external data set in the plurality of external data sets comprising external resources, the external resources within each of the external data sets partitioned among pluralities of external partitions; and a set of computer-executable instructions; and a processing unit, the set of computer-executable instructions, when executed by the processing unit, causes the computing system to: host a plurality of website proxies, each website proxy in the plurality of website proxies associated with a website in the plurality of websites; host a plurality of external data sources, each external data source in the plurality of external data sources associated with a different external data set in the plurality of external data sets; and host a search proxy that: for each given website in the plurality of websites: automatically updates the index such that a given index partition in the plurality of index partitions comprises index entries that map terms in a first set of terms to web pages in the given website that contain terms in the first set of terms, the given website associated with the given index partition; automatically obtains a set of external partition identifiers, each external partition identifier in the set of external partition identifiers identifying external partitions of a given set of external data sources, each external data source in the given set of external data sources being in the plurality of external data sources, each external data source in the given set of external data sources being used by the given website, wherein the search proxy obtains the set of external partition identifiers by: sending a service request to the given website proxy, the given website proxy associated with the given website; and receiving a service response from the given website proxy, the service response comprising the set of external partition identifiers, wherein the given website proxy implements an application programming interface (API) that includes a first method and a second method, wherein the search proxy sends the service request to the given website proxy by invoking the first method and the second method, wherein invoking the first method comprises returning a list of references to each of a plurality of web pages in the given website, wherein invoking the second method comprises returning a copy of one of the plurality of web pages in the given website; and for each given external partition identifier in the set of external partition identifiers, automatically updates the index such that the given index partition comprises index entries that map a second set of terms to external resources in the external partition identified by the given external partition identifier that contain terms in the second set of terms; receives a query request from a querying website proxy in the plurality of website proxies, the query request specifying a query term, the querying website proxy associated with a target website in the plurality of websites; and in response to receiving the query request: automatically identifies a target index partition in the plurality of index partitions, the target website associated with the target index partition; automatically uses index entries in the target index partition to identify a relevant set of resources, each resource in the relevant set of resources containing the query term; and provides a relevant set of resource identifiers to the given website proxy, each resource identifier in the relevant set of resource identifiers identifying a resource in the relevant set of resources.