In my experience, the grinder is not the gating factor on speed. It's learning to overlap preparation steps so you're not just standing there.

Unless you're using a full commercial espresso machine (e.g., La Marzocco GS/3, Speedster, La Spaziale Vivaldi), you have to allow time for the machine to stabilize or your brew temperatures will be way off (trending down or up, depending on the design). A pace of 90 seconds drink-to-drink is about as fast as most semi-commercial/prosumer espresso machine can handle.