diff --git a/doc/backlog.md b/doc/backlog.md
index 9b8d2206..d8eb6021 100644
--- a/doc/backlog.md
+++ b/doc/backlog.md
@@ -48,3 +48,5 @@
 
 **Arch Document:** software design and API document for contributors
 
+**APN:** avoid firebase for iOS and use APN directly
+