diff --git a/includes/server/activities.php b/includes/server/activities.php
index 189a5b8..f7c245e 100644
--- a/includes/server/activities.php
+++ b/includes/server/activities.php
@@ -67,11 +67,33 @@ function persist_activity( $activity ) {
     }
     $activitypub_id = $activity['id'];
     $type = $activity['type'];
-    $wpdb->replace( 'pterotype_activities', array(
-            'activitypub_id' => $activitypub_id,
-            'type' => $type,
-            'activity' => wp_json_encode( $activity )
+    $row = $wpdb->get_row( $wpdb->prepare(
+        'SELECT * FROM pterotype_activities WHERE activitypub_id = %s', $activitypub_id
     ) );
+    $res = true;
+    if ( $row === null ) {
+        $res = $wpdb->insert(
+            'pterotype_activities',
+            array(
+                'activitypub_id' => $activitypub_id,
+                'type' => $type,
+                'activity' => wp_json_encode( $activity )
+            ),
+            '%s'
+        );
+    } else {
+        $res = $wpdb->update(
+            'pterotype_activities',
+            array(
+                'activitypub_id' => $activitypub_id,
+                'type' => $type,
+                'activity' => wp_json_encode( $activity )
+            ),
+            array( 'id' => $row->id ),
+            '%s',
+            '%d'
+        );
+    }
     return $activity;
 }
 
@@ -97,15 +119,16 @@ function create_local_activity( $activity ) {
     $activity_id = $wpdb->insert_id;
     $activity_url = get_rest_url( null, sprintf( '/pterotype/v1/activity/%d', $activity_id ) );
     $activity['id'] = $activity_url;
-    $res = $wpdb->replace(
+    $res = $wpdb->update(
         'pterotype_activities',
         array(
-            'id' => $activity_id,
             'activitypub_id' => $activity_url,
             'type' => $type,
             'activity' => wp_json_encode( $activity ),
         ),
-        array( '%d', '%s', '%s', '%s' )
+        array( 'id' => $activity_id ),
+        '%s',
+        '%d'
     );
     if ( !$res ) {
         return new \WP_Error(
diff --git a/includes/server/actors.php b/includes/server/actors.php
index aa573b3..17558f7 100644
--- a/includes/server/actors.php
+++ b/includes/server/actors.php
@@ -115,10 +115,10 @@ function initialize_actors() {
 
 function create_actor( $slug, $type ) {
     global $wpdb;
-    $wpdb->replace(
-        'pterotype_actors',
-        array( 'slug' => $slug, 'type' => $type ),
-        '%s'
-    );
+    return $wpdb->query( $wpdb->prepare(
+        'INSERT IGNORE INTO pterotype_actors(slug, type) VALUES(%s, %s)',
+        $slug,
+        $type
+    ) );
 }
 ?>
diff --git a/includes/server/following.php b/includes/server/following.php
index 4f18220..0d27f0a 100644
--- a/includes/server/following.php
+++ b/includes/server/following.php
@@ -14,7 +14,8 @@ function request_follow( $actor_id, $object_id ) {
             'actor_id' => $actor_id,
             'object_id' => $object_id,
             'state' => PTEROTYPE_FOLLOW_PENDING
-        )
+        ),
+        array( '%d', '%d', '%s' )
     );
 }
 
diff --git a/includes/server/objects.php b/includes/server/objects.php
index c0e48ff..66c59c2 100644
--- a/includes/server/objects.php
+++ b/includes/server/objects.php
@@ -37,15 +37,16 @@ function create_local_object( $object ) {
     $object['id'] = $object_url;
     $object['likes'] = $object_likes;
     $object['shares'] = $object_shares;
-    $res = $wpdb->replace(
+    $res = $wpdb->update(
         'pterotype_objects',
         array (
-            'id' => $object_id,
             'activitypub_id' => $object_url,
             'type' => $type,
             'object' => wp_json_encode( $object )
         ),
-        array( '%d', '%s', '%s', '%s' )
+        array( 'id' => $object_id ),
+        '%s',
+        '%d'
     );
     if ( !$res ) {
         return new \WP_Error(
@@ -76,7 +77,7 @@ function upsert_object( $object ) {
         );
     }
     $row = $wpdb->get_row( $wpdb->prepare(
-        'SELECT * FROM pterotype_objects WHERE activitypub_url = %s', $object['id']
+        'SELECT * FROM pterotype_objects WHERE activitypub_id = %s', $object['id']
     ) );
     $res = true;
     if ( $row === null ) {
@@ -86,18 +87,20 @@ function upsert_object( $object ) {
                 'activitypub_id' => $object['id'],
                 'type' => $object['type'],
                 'object' => wp_json_encode( $object )
-            )
+            ),
+            '%s'
         );
     } else {
-        $res = $wpdb->replace(
+        $res = $wpdb->update(
             'pterotype_objects',
             array(
-                'id' => $row->id,
                 'activitypub_id' => $object['id'],
                 'type' => $object['type'],
                 'object' => wp_json_encode( $object )
             ),
-            array( '%d', '%s', '%s', '%s' )
+            array( 'id' => $row->id ),
+            '%s',
+            '%d'
         );
         $row = new stdClass();
         $row->id = $wpdb->insert_id;
@@ -219,14 +222,15 @@ function delete_object( $object ) {
     }
     $activitypub_id = $object['id'];
     $tombstone = make_tombstone( $object );
-    $res = $wpdb->replace(
+    $res = $wpdb->update(
         'pterotype_objects',
         array(
-            'activitypub_id' => $activitypub_id,
             'type' => $tombstone['type'],
             'object' => wp_json_encode( $tombstone ),
         ),
-        array( '%s', '%s', '%s' )
+        array( 'activitypub_id' => $activitypub_id ),
+        '%s',
+        '%s'
     );
     if ( !$res ) {
         return new \WP_Error( 'db_error', __( 'Error deleting object', 'pterotype' ) );
diff --git a/includes/server/outbox.php b/includes/server/outbox.php
index 4b6a792..1f6c812 100644
--- a/includes/server/outbox.php
+++ b/includes/server/outbox.php
@@ -25,6 +25,7 @@ require_once plugin_dir_path( __FILE__ ) . 'activities/undo.php';
 require_once plugin_dir_path( __FILE__ ) . '../util.php';
 
 function handle_activity( $actor_slug, $activity ) {
+    xdebug_break();
     // TODO handle authentication/authorization
     $activity = \util\dereference_object( $activity );
     if ( is_wp_error( $activity ) ) {
@@ -113,7 +114,6 @@ function handle_activity( $actor_slug, $activity ) {
         return $activity;
     }
     // the activity may have changed while processing side effects, so persist the new version
-    // TODO why was 'id' missing from the activity here?
     $activity = \activities\persist_activity( $activity );
     if ( is_wp_error( $activity ) ) {
         return $activity;