In some aspects, a methods and systems may combine asynchronous and synchronous messaging infrastructure such that a single system can send messages both asynchronously and synchronously when needed. A system may implement an asynchronous system that is able to determine whether a message should be sent asynchronously or synchronously. If a message is to be sent synchronously, the asynchronous system may emulate a synchronous system by holding a network connection open and/or removing a default callback uniform resource locator (URL) from a data structure used in sending the message.