diff --git a/doc/design/passthrouh_proxy.mdwn b/doc/design/passthrouh_proxy.mdwn
index 6b5063e7df..7860d0f21f 100644
--- a/doc/design/passthrouh_proxy.mdwn
+++ b/doc/design/passthrouh_proxy.mdwn
@@ -88,3 +88,22 @@ The remote interface operates on object files stored on disk. See
 [[todo/transitive_transfers]] for discussion of that problem. If proxies
 get implemented, that problem should be revisited.
 
+## speed
+
+A passthrough proxy should be as fast as possible so as not to add overhead
+to a file retrieve, store, or checkpresent. This probably means that
+it keeps TCP connections open to each host in the cluster. It might use a
+protocol with less overhead than ssh.
+
+In the case of checkpresent, it would be possible for the proxy to not
+communicate with the cluster to check that the data is still present on it.
+As long as all access is intermediated via the proxy, its git-annex branch
+could be relied on to always be correct, in theory. Proving that theory,
+making sure to account for all possible race conditions and other scenarios,
+would be necessary for such an optimisation.
+
+Another way the proxy could speed things up is to cache some subset of
+content. Eg, analize what files are typically requested, and store another
+copy of those on the proxy. Perhaps prioritize storing smaller files, where
+latency tends to swamp transfer speed.
+