diff --git a/example/server/configs.http b/example/server/configs.http
index 5765eed..7ec578c 100644
--- a/example/server/configs.http
+++ b/example/server/configs.http
@@ -4,11 +4,12 @@ GET http://localhost:8080/configs/latest
 
 ### Modify latest config
 PUT http://localhost:8080/configs/latest
-user-id: mark
+user-id: pippo
 
 {
-  "name": "stark",
-  "age": 35
+  "name": "gloria",
+  "age": 38,
+  "friends": ["joe", "mark"]
 }
 
 ### List config versions
diff --git a/streamingconfig.go b/streamingconfig.go
index 75bfe08..65c9527 100644
--- a/streamingconfig.go
+++ b/streamingconfig.go
@@ -71,6 +71,12 @@ func WithCollectionName[T Config](collectionName string) func(repo *WatchedRepo[
 	}
 }
 
+func WithOnUpdate[T Config](onUpdate func(conf T)) func(repo *WatchedRepo[T]) {
+	return func(repo *WatchedRepo[T]) {
+		repo.onUpdate = onUpdate
+	}
+}
+
 type WatchedRepo[T Config] struct {
 	lgr             *slog.Logger
 	source          *mongo.Database
@@ -82,6 +88,7 @@ type WatchedRepo[T Config] struct {
 	skipIndexOperation bool
 	configs            *mongo.Collection
 	started            bool
+	onUpdate           func(conf T)
 }
 
 func NewWatchedRepo[T Config](
@@ -419,6 +426,9 @@ func (s *WatchedRepo[T]) iterateChangeStream(ctx context.Context, cs *mongo.Chan
 				if s.cfgWithDefaults, err = copyAndSetDefaults(s.cfg); err != nil {
 					s.lgr.With("error", err).ErrorContext(ctx, "could not set defaults")
 				}
+				if s.onUpdate != nil {
+					s.onUpdate(s.cfgWithDefaults.Config)
+				}
 			default:
 				s.lgr.With("operationType", dto.OperationType).ErrorContext(ctx, "invalid or unexpected operation")
 				continue
diff --git a/streamingconfig_integration_test.go b/streamingconfig_integration_test.go
index 1ce039d..5bd4717 100644
--- a/streamingconfig_integration_test.go
+++ b/streamingconfig_integration_test.go
@@ -78,15 +78,15 @@ func (a *appConfigV1) validate() error {
 
 func NewTestStore[T config.Config](
 	t *testing.T,
-	nowProvider func() time.Time,
 	db *mongo.Database,
+	opts ...func(repo *config.WatchedRepo[T]),
 ) *config.WatchedRepo[T] {
 	t.Helper()
 	configStore, err := config.NewWatchedRepo(
 		config.Args{
 			Logger: slog.Default(),
 			DB:     db,
-		}, config.WithNowFn[T](nowProvider))
+		}, opts...)
 	require.NoError(t, err)
 
 	return configStore
@@ -120,7 +120,7 @@ func newFixture(t *testing.T) *fixture {
 		assert.NoError(t, client.Database("admin").
 			RunCommand(ctx, bson.D{primitive.E{Key: "isMaster", Value: 1}}).Decode(&result), "checking mongoDB primary status")
 		assert.Equal(t, true, result["ismaster"])
-	}, 15*time.Second, 100*time.Millisecond)
+	}, 30*time.Second, 100*time.Millisecond)
 
 	return &fixture{db: db}
 }
@@ -145,7 +145,7 @@ func Test_ConfigCreateFindAndUpdateConfiguration(t *testing.T) {
 	}
 	ctx, cnl := context.WithTimeout(context.Background(), 30*time.Second)
 
-	configStoreOne := NewTestStore[*appConfigV0](t, nowProvider, f.db)
+	configStoreOne := NewTestStore[*appConfigV0](t, f.db, config.WithNowFn[*appConfigV0](nowProvider))
 	t.Run("cannot perform methods before starting", func(t *testing.T) {
 		cfg, err := configStoreOne.GetConfig()
 		require.ErrorIs(t, err, config.ErrNotStarted)
@@ -158,7 +158,7 @@ func Test_ConfigCreateFindAndUpdateConfiguration(t *testing.T) {
 	done1, err := configStoreOne.Start(ctx)
 	require.NoError(t, err)
 
-	configStoreTwo := NewTestStore[*appConfigV0](t, nowProvider, f.db)
+	configStoreTwo := NewTestStore[*appConfigV0](t, f.db, config.WithNowFn[*appConfigV0](nowProvider))
 	done2, err := configStoreTwo.Start(ctx)
 	require.NoError(t, err)
 	t.Cleanup(func() {
@@ -287,6 +287,44 @@ func Test_ConfigCreateFindAndUpdateConfiguration(t *testing.T) {
 				require.Len(t, configsByVersion, 0)
 			})
 		})
+
+		t.Run("on update", func(t *testing.T) {
+			var cfg *appConfigV0
+			configStore3 := NewTestStore[*appConfigV0](
+				t,
+				f.db,
+				config.WithNowFn[*appConfigV0](nowProvider),
+				config.WithOnUpdate[*appConfigV0](func(conf *appConfigV0) {
+					cfg = conf
+				}),
+			)
+			done2, err := configStore3.Start(ctx)
+			require.NoError(t, err)
+			t.Cleanup(func() {
+				cnl()
+				doneOrTimeout(t, done1, 5*time.Second)
+				doneOrTimeout(t, done2, 5*time.Second)
+			})
+
+			now = &at
+			setV3 := &appConfigV0{
+				Name:     "n3",
+				Duration: 3 * time.Second,
+				Time:     at.Add(3 * time.Second),
+				Nested:   nestedConfig{Counter: 5},
+				List:     []string{"e", "f", "d"},
+			}
+			cV3, err := configStoreTwo.UpdateConfig(ctx, config.UpdateConfigCmd[*appConfigV0]{
+				By:     "u2",
+				Config: setV3,
+			})
+			require.NoError(t, err)
+
+			require.EventuallyWithT(t, func(t *assert.CollectT) {
+				assert.Equal(t, cV3.Config, cfg)
+			}, 5*time.Second, 100*time.Millisecond)
+
+		})
 	})
 }
 
@@ -302,11 +340,19 @@ func Test_ConfigBackwardCompatibility(t *testing.T) {
 	}
 	ctx, cnl := context.WithTimeout(context.Background(), 30*time.Second)
 
-	configStoreOne := NewTestStore[*appConfigV0](t, nowProvider, f.db)
+	configStoreOne := NewTestStore[*appConfigV0](
+		t,
+		f.db,
+		config.WithNowFn[*appConfigV0](nowProvider),
+	)
 	done1, err := configStoreOne.Start(ctx)
 	require.NoError(t, err)
 
-	configStoreTwo := NewTestStore[*appConfigV1](t, nowProvider, f.db)
+	configStoreTwo := NewTestStore[*appConfigV1](
+		t,
+		f.db,
+		config.WithNowFn[*appConfigV1](nowProvider),
+	)
 	done2, err := configStoreTwo.Start(ctx)
 	require.NoError(t, err)
 	t.Cleanup(func() {