The 2D Classification step also shows scaling only up to 2 GPUs. At present, EC2 instances are available with 1, 4, or 8 GPUs, so a 4-GPU instance is recommended (e.g. p3.8xlarge). Optionally, a lower-cost instance like the g4dn.metal (with 8 GPUs) may be used, with the expectation that scaling may be limited. The performance difference is minimal across GPU architectures, so price should be the driving factor in choosing an instance for this stage.