Web services hosted at a data center may employ architectural patterns that tend to obfuscate the source of queries made against databases and other resources in the data center. The queries may be the source of performance, capacity or utilization problems, and may contribute to the cost of hosting the web service. Web service invocations may be associated with identifiers that can be included in modified queries sent to databases and other resources. Summarized cost information may be calculated based on recorded associations between the identifiers and query performance information.