Abstract: Methods, systems, and computer-storage media having computer-executable instructions embodied thereon that, when executed, perform methods in accordance with embodiments hereof, for batching requests into calls. Initially, an indication to present a web page is sent from an input device that triggers a web browser to download and execute source code underlying the requested web page. The executed source code instructs the web browser to send one or more ad-selection requests to an ad-delivering engine. The web browser batches the ad-selection selection requests into a retrieval call such that the ad-selection requests are communicated concurrently. The ad-delivering engine parses the retrieval request, extracts parameters from the parsed ad-selection requests, distributes the parameters to back-end servers, and batches location indicators of advertisements that correspond to the parameters into a response call.