diff --git a/prototypes/quic_demo/README.md b/prototypes/quic_demo/README.md
index e28d8f4..484af59 100644
--- a/prototypes/quic_demo/README.md
+++ b/prototypes/quic_demo/README.md
@@ -55,6 +55,14 @@ The command types are:
 | 11   | P3     | P4          | Relay tells server that a client wants to connect |
 | 12   | P2     | P4 (via P3) | Client wants a port forwarded from the server     |
 
+# Performance
+
+Running all 5 processes on my desktop, measured by `pv`, I can hit 10 MiB/s
+for bulk transfers with debug builds, and 100 MiB/s with release builds.
+In production, P2, P3, and P4 would be running on separate systems, and the
+bottleneck would likely be the Internet connection between P2 and P3 or between
+P3 and P4.
+
 # Plan
 
 This is a TCP port forwarding system, like SSH has, but better.