BNB Chain's recent post-quantum upgrade test achieved full backward compatibility but resulted in a 40% reduction in cross-region transactions per second. The test, detailed in a migration report, evaluated cryptographic changes designed to withstand future quantum attacks. While maintaining unchanged RPCs, SDKs, and wallet addresses, the test revealed significant infrastructure overhead, with transaction signature sizes increasing from 65 bytes to 2,420 bytes. The throughput decline poses challenges for BNB Chain, known for its high-frequency DeFi trades and on-chain games. The network faces hurdles in scaling its data layer to accommodate the increased block sizes and propagation times. Despite the performance hit, the upgrade offers a quantum-safe path without requiring users to generate new keys or manage separate wallets. However, the timeline for production deployment remains uncertain, as engineers work to reduce data overhead and explore scaling innovations.