To encode fast auditory signals in the auditory brainstem, the reliable and synchronized transmitter release from presynaptic terminals is critical. At the calyx of Held synapse, the synaptic delay and time course of transmitter release become accelerated during the developmental period of hearing acquisition. To address how the distance between voltage-gated Ca²⁺ channels (VGCCs) and synaptic vesicles (SVs) contribute to this change, we used numerical simulations of a Ca²⁺ reaction-diffusion model, combined with a SV release model. Our simulations, taking account into single channel current and channel open probability, indicate that the presence of a VGCC cluster in the active zone is essential for reliable, i.e. high efficacy neurotransmission in response to single action potentials. The time course of transmitter release can be reproduced by simulation assuming that SVs are located at several tens of nanometers from the perimeter of VGCC clusters. In this topographical arrangement, shortening the SV-VGCC perimeter coupling distance from 30 to 20 nm reproduced the developmental acceleration of the release time course. Furthermore this SV-VGCC topographical arrangement could reproduce the time course of multiple release components observed at this synapse in response to step depolarizations. We conclude that the SV-VGCC perimeter coupling distance critically determines the time course of SV transmitter release, and propose that the different release time courses can arise from different VGCC-SV perimeter coupling distances.