diff --git a/src/database/abstraction/heed.rs b/src/database/abstraction/heed.rs
index 9cca0975..8f577020 100644
--- a/src/database/abstraction/heed.rs
+++ b/src/database/abstraction/heed.rs
@@ -9,7 +9,7 @@ use std::{
     sync::{Arc, Mutex},
 };
 
-use super::{DatabaseEngine, Tree};
+use super::{KeyValueDatabaseEngine, KvTree};
 
 type TupleOfBytes = (Vec<u8>, Vec<u8>);
 
@@ -30,8 +30,8 @@ fn convert_error(error: heed::Error) -> Error {
     }
 }
 
-impl DatabaseEngine for Engine {
-    fn open(config: &Config) -> Result<Arc<Self>> {
+impl KeyValueDatabaseEngine for Arc<Engine> {
+    fn open(config: &Config) -> Result<Self> {
         let mut env_builder = heed::EnvOpenOptions::new();
         env_builder.map_size(1024 * 1024 * 1024 * 1024); // 1 Terabyte
         env_builder.max_readers(126);
@@ -49,10 +49,10 @@ impl DatabaseEngine for Engine {
         }))
     }
 
-    fn open_tree(self: &Arc<Self>, name: &'static str) -> Result<Arc<dyn Tree>> {
+    fn open_tree(&self, name: &'static str) -> Result<Arc<dyn KvTree>> {
         // Creates the db if it doesn't exist already
         Ok(Arc::new(EngineTree {
-            engine: Arc::clone(self),
+            engine: self.clone(),
             tree: Arc::new(
                 self.env
                     .create_database(Some(name))
@@ -62,7 +62,7 @@ impl DatabaseEngine for Engine {
         }))
     }
 
-    fn flush(self: &Arc<Self>) -> Result<()> {
+    fn flush(&self) -> Result<()> {
         self.env.force_sync().map_err(convert_error)?;
         Ok(())
     }
@@ -78,17 +78,7 @@ impl EngineTree {
         let (s, r) = bounded::<TupleOfBytes>(100);
         let engine = Arc::clone(&self.engine);
 
-        let lock = self.engine.iter_pool.lock().await;
-        if lock.active_count() < lock.max_count() {
-            lock.execute(move || {
-                iter_from_thread_work(tree, &engine.env.read_txn().unwrap(), from, backwards, &s);
-            });
-        } else {
-            std::thread::spawn(move || {
-                iter_from_thread_work(tree, &engine.env.read_txn().unwrap(), from, backwards, &s);
-            });
-        }
-
+        let lock = self.engine.iter_pool.lock();
         Box::new(r.into_iter())
     }
 }
@@ -123,7 +113,7 @@ fn iter_from_thread_work(
     }
 }
 
-impl Tree for EngineTree {
+impl KvTree for EngineTree {
     fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>> {
         let txn = self.engine.env.read_txn().map_err(convert_error)?;
         Ok(self
@@ -143,6 +133,36 @@ impl Tree for EngineTree {
         Ok(())
     }
 
+    fn insert_batch<'a>(&self, iter: &mut dyn Iterator<Item = (Vec<u8>, Vec<u8>)>) -> Result<()> {
+        let mut txn = self.engine.env.write_txn().map_err(convert_error)?;
+        for (key, value) in iter {
+            self.tree
+                .put(&mut txn, &key.as_slice(), &value.as_slice())
+                .map_err(convert_error)?;
+            self.watchers.wake(&key);
+        }
+        txn.commit().map_err(convert_error)?;
+        Ok(())
+    }
+
+    fn increment_batch<'a>(&self, iter: &mut dyn Iterator<Item = Vec<u8>>) -> Result<()> {
+        let mut txn = self.engine.env.write_txn().map_err(convert_error)?;
+        for key in iter {
+            let old = self
+                .tree
+                .get(&txn, &key.as_slice())
+                .map_err(convert_error)?;
+            let new = crate::utils::increment(old.as_deref())
+                .expect("utils::increment always returns Some");
+
+            self.tree
+                .put(&mut txn, &key.as_slice(), &&*new)
+                .map_err(convert_error)?;
+        }
+        txn.commit().map_err(convert_error)?;
+        Ok(())
+    }
+
     fn remove(&self, key: &[u8]) -> Result<()> {
         let mut txn = self.engine.env.write_txn().map_err(convert_error)?;
         self.tree.delete(&mut txn, &key).map_err(convert_error)?;
@@ -150,7 +170,7 @@ impl Tree for EngineTree {
         Ok(())
     }
 
-    fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a> {
+    fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + 'a> {
         self.iter_from(&[], false)
     }
 
@@ -158,7 +178,7 @@ impl Tree for EngineTree {
         &self,
         from: &[u8],
         backwards: bool,
-    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send> {
+    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)>> {
         self.iter_from_thread(Arc::clone(&self.tree), from.to_vec(), backwards)
     }
 
@@ -181,7 +201,7 @@ impl Tree for EngineTree {
     fn scan_prefix<'a>(
         &'a self,
         prefix: Vec<u8>,
-    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + Send + 'a> {
+    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + 'a> {
         Box::new(
             self.iter_from(&prefix, false)
                 .take_while(move |(key, _)| key.starts_with(&prefix)),
diff --git a/src/utils/error.rs b/src/utils/error.rs
index 1d811106..4be3fbab 100644
--- a/src/utils/error.rs
+++ b/src/utils/error.rs
@@ -164,7 +164,7 @@ impl Error {
             #[cfg(feature = "persy")]
             Self::PersyError { .. } => db_error,
             #[cfg(feature = "heed")]
-            Self::HeedError => db_error,
+            Self::HeedError { .. } => db_error,
             #[cfg(feature = "rocksdb")]
             Self::RocksDbError { .. } => db_error,
             Self::IoError { .. } => db_error,