diff --git a/journal/2021-06-06--13-43-12Z--service_oriented_programming.org b/journal/2021-06-06--13-43-12Z--service_oriented_programming.org
index 2c182446..3a6c1cd7 100644
--- a/journal/2021-06-06--13-43-12Z--service_oriented_programming.org
+++ b/journal/2021-06-06--13-43-12Z--service_oriented_programming.org
@@ -57,6 +57,7 @@ The component will form an acyclic graph of dependencies.
 Principles:
 
 A service contain an internal state.
+Every service has at most single instance for the entire Application.
 Every method of the service can access this internal state.
 No OOP is needed, only functions.