TLS doesn't really add latency on top of TCP after you make the initial connection - it mostly adds a bit of extra processing overhead for encryption. HFT firms

TLS doesn't really add latency on top of TCP after you make the initial connection - it mostly adds a bit of extra processing overhead for encryption. HFT firms aren't usually encryption-bandwidth-constrained. I'm not actually sure if most exchange FIX connections or whatever actually run over TLS, but that would be reasonable.