diff --git a/src/operation_dispatcher.rs b/src/operation_dispatcher.rs
index fa0b5a8..c656058 100644
--- a/src/operation_dispatcher.rs
+++ b/src/operation_dispatcher.rs
@@ -48,7 +48,7 @@ impl Operation {
     pub fn new(extension: Rc<Extension>, procedure: Procedure) -> Self {
         Self {
             state: State::Pending,
-            result: Err(Status::Empty),
+            result: Ok(0), // Heuristics: zero represents that it's not been triggered, following `hostcalls` example
             extension,
             procedure,
             grpc_call_fn,
@@ -56,15 +56,22 @@ impl Operation {
         }
     }
 
-    fn trigger(&mut self) {
-        if let State::Done = self.state {
-        } else {
-            self.result = self.procedure.0.send(
-                self.get_map_values_bytes_fn,
-                self.grpc_call_fn,
-                self.procedure.1.clone(),
-            );
-            self.state.next();
+    fn trigger(&mut self) -> Result<u32, Status> {
+        match self.state {
+            State::Pending => {
+                self.result = self.procedure.0.send(
+                    self.get_map_values_bytes_fn,
+                    self.grpc_call_fn,
+                    self.procedure.1.clone(),
+                );
+                self.state.next();
+                self.result
+            }
+            State::Waiting => {
+                self.state.next();
+                self.result
+            }
+            State::Done => self.result,
         }
     }
 
@@ -88,6 +95,7 @@ impl Operation {
 #[allow(dead_code)]
 pub struct OperationDispatcher {
     operations: RefCell<Vec<Operation>>,
+    waiting_operations: RefCell<HashMap<u32, Operation>>, // TODO(didierofrivia): Maybe keep references or Rc
     service_handlers: HashMap<String, Rc<GrpcServiceHandler>>,
 }
 
@@ -96,6 +104,7 @@ impl OperationDispatcher {
     pub fn default() -> Self {
         OperationDispatcher {
             operations: RefCell::new(vec![]),
+            waiting_operations: RefCell::new(HashMap::default()),
             service_handlers: HashMap::default(),
         }
     }
@@ -103,6 +112,7 @@ impl OperationDispatcher {
         Self {
             service_handlers,
             operations: RefCell::new(vec![]),
+            waiting_operations: RefCell::new(HashMap::new()),
         }
     }
 
@@ -148,10 +158,18 @@ impl OperationDispatcher {
         let mut operations = self.operations.borrow_mut();
         if let Some((i, operation)) = operations.iter_mut().enumerate().next() {
             if let State::Done = operation.get_state() {
+                if let Ok(token_id) = operation.result {
+                    self.waiting_operations.borrow_mut().remove(&token_id);
+                } // If result was Err, means the operation wasn't indexed
+
                 operations.remove(i);
                 operations.get(i).cloned() // The next op is now at `i`
             } else {
-                operation.trigger();
+                if let Ok(token_id) = operation.trigger() {
+                    self.waiting_operations
+                        .borrow_mut()
+                        .insert(token_id, operation.clone());
+                } // TODO(didierofrivia): Decide on indexing the failed operations.
                 Some(operation.clone())
             }
         } else {
@@ -223,7 +241,7 @@ mod tests {
     fn build_operation() -> Operation {
         Operation {
             state: State::Pending,
-            result: Ok(1),
+            result: Ok(0),
             extension: Rc::new(Extension::default()),
             procedure: (
                 Rc::new(build_grpc_service_handler()),
@@ -241,16 +259,19 @@ mod tests {
         assert_eq!(operation.get_state(), State::Pending);
         assert_eq!(operation.get_extension_type(), ExtensionType::RateLimit);
         assert_eq!(operation.get_failure_mode(), FailureMode::Deny);
-        assert_eq!(operation.get_result(), Ok(1));
+        assert_eq!(operation.get_result(), Ok(0));
     }
 
     #[test]
     fn operation_transition() {
         let mut operation = build_operation();
+        assert_eq!(operation.result, Ok(0));
         assert_eq!(operation.get_state(), State::Pending);
-        operation.trigger();
+        let mut res = operation.trigger();
+        assert_eq!(res, Ok(200));
         assert_eq!(operation.get_state(), State::Waiting);
-        operation.trigger();
+        res = operation.trigger();
+        assert_eq!(res, Ok(200));
         assert_eq!(operation.result, Ok(200));
         assert_eq!(operation.get_state(), State::Done);
     }
@@ -280,27 +301,43 @@ mod tests {
         let operation_dispatcher = OperationDispatcher::default();
         operation_dispatcher.push_operations(vec![build_operation(), build_operation()]);
 
-        assert_eq!(operation_dispatcher.get_current_operation_result(), Ok(1));
+        assert_eq!(operation_dispatcher.get_current_operation_result(), Ok(0));
         assert_eq!(
             operation_dispatcher.get_current_operation_state(),
             Some(State::Pending)
         );
+        assert_eq!(
+            operation_dispatcher.waiting_operations.borrow_mut().len(),
+            0
+        );
 
         let mut op = operation_dispatcher.next();
         assert_eq!(op.clone().unwrap().get_result(), Ok(200));
         assert_eq!(op.unwrap().get_state(), State::Waiting);
+        assert_eq!(
+            operation_dispatcher.waiting_operations.borrow_mut().len(),
+            1
+        );
 
         op = operation_dispatcher.next();
         assert_eq!(op.clone().unwrap().get_result(), Ok(200));
         assert_eq!(op.unwrap().get_state(), State::Done);
 
         op = operation_dispatcher.next();
-        assert_eq!(op.clone().unwrap().get_result(), Ok(1));
+        assert_eq!(op.clone().unwrap().get_result(), Ok(0));
         assert_eq!(op.unwrap().get_state(), State::Pending);
+        assert_eq!(
+            operation_dispatcher.waiting_operations.borrow_mut().len(),
+            0
+        );
 
         op = operation_dispatcher.next();
         assert_eq!(op.clone().unwrap().get_result(), Ok(200));
         assert_eq!(op.unwrap().get_state(), State::Waiting);
+        assert_eq!(
+            operation_dispatcher.waiting_operations.borrow_mut().len(),
+            1
+        );
 
         op = operation_dispatcher.next();
         assert_eq!(op.clone().unwrap().get_result(), Ok(200));
@@ -309,5 +346,9 @@ mod tests {
         op = operation_dispatcher.next();
         assert!(op.is_none());
         assert!(operation_dispatcher.get_current_operation_state().is_none());
+        assert_eq!(
+            operation_dispatcher.waiting_operations.borrow_mut().len(),
+            0
+        );
     }
 }