diff --git a/doc/DATABASE.md b/doc/DATABASE.md
index 6c4920b..f38cc07 100644
--- a/doc/DATABASE.md
+++ b/doc/DATABASE.md
@@ -1,5 +1,10 @@
 # Database structure of hashlookup
 
+## hash storage
+
+- `l:<md5>` set -> {sha1, sha1}
+- `h:<sha1>`` hash -> keys from NSRL or other data sources
+
 ## Publish-Subscribe channels
 
 - `nx` JSON message of non-existing hashes searched