  We show that the steady-state distribution of the join-the-shortest-queue
(JSQ) system converges, in the Halfin-Whitt regime, to its diffusion limit at a
rate of at least $1/\sqrt{n}$, where $n$ is the number of servers. Our proof
uses Stein's method and, specifically, the recently proposed prelimit generator
comparison approach. The JSQ system is non-trivial, high-dimensional, and has a
state-space collapse component, and our analysis may serve as a helpful example
to readers wishing to apply the approach to their own setting.
