diff --git a/src/task_monitor.rs b/src/task_monitor.rs
index 03654287..e36d8828 100644
--- a/src/task_monitor.rs
+++ b/src/task_monitor.rs
@@ -4,7 +4,7 @@ use std::time::Duration;
 use clap::Parser;
 use once_cell::sync::Lazy;
 use prometheus::{linear_buckets, register_gauge, register_histogram, Gauge, Histogram};
-use tokio::sync::{broadcast, mpsc, Notify, RwLock};
+use tokio::sync::{broadcast, mpsc, Mutex, Notify, RwLock};
 use tokio::task::JoinHandle;
 use tracing::{info, instrument, warn};
 
@@ -197,6 +197,8 @@ impl TaskMonitor {
         // in the database
         wake_up_notify.notify_one();
 
+        let pending_insertion_mutex = Arc::new(Mutex::new(()));
+
         let mut handles = Vec::new();
 
         // Finalize identities task
@@ -252,6 +254,7 @@ impl TaskMonitor {
             self.database.clone(),
             self.tree_state.get_latest_tree(),
             wake_up_notify.clone(),
+            pending_insertion_mutex.clone(),
         );
 
         let insert_identities_handle = crate::utils::spawn_monitored_with_backoff(
@@ -269,6 +272,7 @@ impl TaskMonitor {
             self.batch_deletion_timeout_seconds,
             self.min_batch_deletion_size,
             wake_up_notify,
+            pending_insertion_mutex,
         );
 
         let delete_identities_handle = crate::utils::spawn_monitored_with_backoff(
diff --git a/src/task_monitor/tasks/delete_identities.rs b/src/task_monitor/tasks/delete_identities.rs
index b21779bd..02f7e343 100644
--- a/src/task_monitor/tasks/delete_identities.rs
+++ b/src/task_monitor/tasks/delete_identities.rs
@@ -2,7 +2,7 @@ use std::collections::HashSet;
 use std::sync::Arc;
 
 use chrono::Utc;
-use tokio::sync::Notify;
+use tokio::sync::{Mutex, Notify};
 use tracing::info;
 
 use crate::database::types::DeletionEntry;
@@ -10,11 +10,12 @@ use crate::database::Database;
 use crate::identity_tree::{Hash, Latest, TreeVersion};
 
 pub struct DeleteIdentities {
-    database:                Arc<Database>,
-    latest_tree:             TreeVersion<Latest>,
-    deletion_time_interval:  i64,
-    min_deletion_batch_size: usize,
-    wake_up_notify:          Arc<Notify>,
+    database:                 Arc<Database>,
+    latest_tree:              TreeVersion<Latest>,
+    deletion_time_interval:   i64,
+    min_deletion_batch_size:  usize,
+    wake_up_notify:           Arc<Notify>,
+    pending_insertions_mutex: Arc<Mutex<()>>,
 }
 
 impl DeleteIdentities {
@@ -24,6 +25,7 @@ impl DeleteIdentities {
         deletion_time_interval: i64,
         min_deletion_batch_size: usize,
         wake_up_notify: Arc<Notify>,
+        pending_insertions_mutex: Arc<Mutex<()>>,
     ) -> Arc<Self> {
         Arc::new(Self {
             database,
@@ -31,6 +33,7 @@ impl DeleteIdentities {
             deletion_time_interval,
             min_deletion_batch_size,
             wake_up_notify,
+            pending_insertions_mutex,
         })
     }
 
@@ -41,6 +44,7 @@ impl DeleteIdentities {
             self.deletion_time_interval,
             self.min_deletion_batch_size,
             self.wake_up_notify.clone(),
+            &self.pending_insertions_mutex,
         )
         .await
     }
@@ -52,6 +56,7 @@ async fn delete_identities(
     deletion_time_interval: i64,
     min_deletion_batch_size: usize,
     wake_up_notify: Arc<Notify>,
+    pending_insertions_mutex: &Mutex<()>,
 ) -> anyhow::Result<()> {
     info!("Starting deletion processor.");
 
@@ -89,6 +94,8 @@ async fn delete_identities(
                 "Length mismatch when appending identities to tree"
             );
 
+            let _guard = pending_insertions_mutex.lock().await;
+
             // Insert the new items into pending identities
             let items = data.into_iter().zip(leaf_indices);
             for ((root, _proof), leaf_index) in items {
diff --git a/src/task_monitor/tasks/insert_identities.rs b/src/task_monitor/tasks/insert_identities.rs
index 10fc65f7..2d6cc89d 100644
--- a/src/task_monitor/tasks/insert_identities.rs
+++ b/src/task_monitor/tasks/insert_identities.rs
@@ -1,7 +1,7 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use tokio::sync::Notify;
+use tokio::sync::{Mutex, Notify};
 use tokio::time::sleep;
 use tracing::instrument;
 
@@ -10,9 +10,10 @@ use crate::database::Database;
 use crate::identity_tree::{Latest, TreeVersion, TreeVersionReadOps, UnprocessedStatus};
 
 pub struct InsertIdentities {
-    database:       Arc<Database>,
-    latest_tree:    TreeVersion<Latest>,
-    wake_up_notify: Arc<Notify>,
+    database:                 Arc<Database>,
+    latest_tree:              TreeVersion<Latest>,
+    wake_up_notify:           Arc<Notify>,
+    pending_insertions_mutex: Arc<Mutex<()>>,
 }
 
 impl InsertIdentities {
@@ -20,16 +21,24 @@ impl InsertIdentities {
         database: Arc<Database>,
         latest_tree: TreeVersion<Latest>,
         wake_up_notify: Arc<Notify>,
+        pending_insertions_mutex: Arc<Mutex<()>>,
     ) -> Arc<Self> {
         Arc::new(Self {
             database,
             latest_tree,
             wake_up_notify,
+            pending_insertions_mutex,
         })
     }
 
     pub async fn run(self: Arc<Self>) -> anyhow::Result<()> {
-        insert_identities_loop(&self.database, &self.latest_tree, &self.wake_up_notify).await
+        insert_identities_loop(
+            &self.database,
+            &self.latest_tree,
+            &self.wake_up_notify,
+            &self.pending_insertions_mutex,
+        )
+        .await
     }
 }
 
@@ -37,6 +46,7 @@ async fn insert_identities_loop(
     database: &Database,
     latest_tree: &TreeVersion<Latest>,
     wake_up_notify: &Notify,
+    pending_insertions_mutex: &Mutex<()>,
 ) -> anyhow::Result<()> {
     loop {
         // get commits from database
@@ -48,7 +58,7 @@ async fn insert_identities_loop(
             continue;
         }
 
-        insert_identities(database, latest_tree, unprocessed).await?;
+        insert_identities(database, latest_tree, unprocessed, pending_insertions_mutex).await?;
         // Notify the identity processing task, that there are new identities
         wake_up_notify.notify_one();
     }
@@ -59,6 +69,7 @@ async fn insert_identities(
     database: &Database,
     latest_tree: &TreeVersion<Latest>,
     identities: Vec<UnprocessedCommitment>,
+    pending_insertions_mutex: &Mutex<()>,
 ) -> anyhow::Result<()> {
     // Filter out any identities that are already in the `identities` table
     let mut filtered_identities = vec![];
@@ -96,6 +107,8 @@ async fn insert_identities(
 
     let items = data.into_iter().zip(filtered_identities);
 
+    let _guard = pending_insertions_mutex.lock().await;
+
     for ((root, _proof, leaf_index), identity) in items {
         database
             .insert_pending_identity(leaf_index, &identity, &root)