Is your real-time payment system ready for peak demand? Speed is promised, but sustained performance under immense pressure builds trust. Unforeseen transaction spikes or system bottlenecks can cripple operations, causing economic risks. This article reveals how sandbox environments are critical for rigorous performance testing. Simulate thousands of transactions per second, identify hidden bottlenecks, and test resilience against real-world degradation. Learn how sandboxes enable robust capacity planning and cross-rail benchmarking, ensuring your system delivers consistently low latency and high availability. Don't just plan for speed; prepare for pressure.