pqc-bench Part 2: X25519MLKEM768 overhead drops to 1 ms with session resumption

Phase 2 of the pqc-bench benchmark on Graviton3 shows that with session caching and connection pooling, the hybrid X25519MLKEM768 key exchange adds just 1 ms at p95 for fresh TLS 1.3 connections and nothing for resumed ones. At the record layer, classical and PQ crypto are indistinguishable up to 100 KB responses.

• Fresh PQ connections add 1 ms at p95; resumed ones show zero overhead
• Session resumption saves 3–4 ms at p95, outweighing the PQ cost
• p95 is identical for classical and PQ at 100 B, 10 KB and 100 KB payloads
• The 1 MB test failed: c7g.large hit its 0.75 Gbps NIC baseline