Techniques are described for managing data transmissions between computing systems based at least in part on using a streaming transport protocol. At least some such data transmissions may be performed using HTTP, with one or more underlying transport protocols used to implement the HTTP-based data transmissions. HTTP-based data transmissions performed using an underlying streaming transport protocol, for example, may send data without performing error detection for reliability and without ensuring ordered delivery of the sent data. In addition, one or more HTTP-based data transmissions may be initiated using an underlying streaming transport protocol, but subsequent data transmissions may switch to using a different underlying transport protocol (e.g., TCP) or different transmission technique that is performed without using data streaming.