diff --git a/services/outputhost/messagecache.go b/services/outputhost/messagecache.go
index bb6916ec..f171833b 100644
--- a/services/outputhost/messagecache.go
+++ b/services/outputhost/messagecache.go
@@ -155,7 +155,7 @@ const (
 	stateProgressing
 )
 
-const ackChannelSize = 10000
+const ackChannelSize = 1000
 
 // AckID is an acknowledgement ID; not the same as common.AckID, which decomposes this string
 // Capitalized because otherwise the type name conflicts horribly with local variables
diff --git a/services/outputhost/outputhost.go b/services/outputhost/outputhost.go
index d71d0c8b..87cc58e1 100644
--- a/services/outputhost/outputhost.go
+++ b/services/outputhost/outputhost.go
@@ -53,7 +53,7 @@ import (
 const (
 	// defaultIdleTimeout is the time to wait before we close all streams
 	defaultIdleTimeout        = 10 * time.Minute
-	defaultPrefetchBufferSize = 10000 // XXX: find the optimal prefetch buffer size
+	defaultPrefetchBufferSize = 1000 // XXX: find the optimal prefetch buffer size
 	defaultUnloadChSize       = 50
 	defaultAckMgrMapChSize    = 500
 	defaultAckMgrIDStartFrom  = 0                // the default ack mgr id for this host to start from