diff --git a/app/state.go b/app/state.go
index b0c358e..2edb323 100644
--- a/app/state.go
+++ b/app/state.go
@@ -5,3 +5,11 @@ type State struct {
 	// Last processed block
 	CurrentBlock uint32
 }
+
+type (
+	// StateLoader is a function that loads a state.
+	StateLoader func(*State)
+
+	// StateSaver is a function that saves a state.
+	StateSaver func(State) error
+)