diff --git a/aiida/backends/general/migrations/utils.py b/aiida/backends/general/migrations/utils.py
index 734f40839a..e947276282 100644
--- a/aiida/backends/general/migrations/utils.py
+++ b/aiida/backends/general/migrations/utils.py
@@ -15,7 +15,7 @@
 import os
 import pathlib
 import re
-import typing
+from typing import Dict, Iterable, List, Optional, Union
 
 from disk_objectstore import Container
 from disk_objectstore.utils import LazyOpener
@@ -42,8 +42,8 @@ def __init__(
         self,
         name: str = '',
         file_type: FileType = FileType.DIRECTORY,
-        key: typing.Union[str, None, LazyOpener] = None,
-        objects: typing.Dict[str, 'File'] = None
+        key: Union[str, None, LazyOpener] = None,
+        objects: Dict[str, 'File'] = None
     ):
         # pylint: disable=super-init-not-called
         if not isinstance(name, str):
@@ -86,43 +86,37 @@ class NoopRepositoryBackend(AbstractRepositoryBackend):
     """
 
     @property
-    def uuid(self) -> typing.Optional[str]:
+    def uuid(self) -> Optional[str]:
         """Return the unique identifier of the repository.
 
         .. note:: A sandbox folder does not have the concept of a unique identifier and so always returns ``None``.
         """
         return None
 
-    def initialise(self, **kwargs) -> None:
-        """Initialise the repository if it hasn't already been initialised.
+    @property
+    def key_format(self) -> Optional[str]:
+        return None
 
-        :param kwargs: parameters for the initialisation.
-        """
+    def initialise(self, **kwargs) -> None:
         raise NotImplementedError()
 
     @property
     def is_initialised(self) -> bool:
-        """Return whether the repository has been initialised."""
         return True
 
     def erase(self):
         raise NotImplementedError()
 
     def _put_object_from_filelike(self, handle: io.BufferedIOBase) -> str:
-        """Store the byte contents of a file in the repository.
-
-        :param handle: filelike object with the byte content to be stored.
-        :return: the generated fully qualified identifier for the object within the repository.
-        :raises TypeError: if the handle is not a byte stream.
-        """
         return LazyOpener(handle.name)
 
-    def has_object(self, key: str) -> bool:
-        """Return whether the repository has an object with the given key.
+    def has_objects(self, keys: List[str]) -> List[bool]:
+        raise NotImplementedError()
 
-        :param key: fully qualified identifier for the object within the repository.
-        :return: True if the object exists, False otherwise.
-        """
+    def delete_objects(self, keys: List[str]) -> None:
+        raise NotImplementedError()
+
+    def list_objects(self) -> Iterable[str]:
         raise NotImplementedError()
 
 
diff --git a/aiida/repository/backend/abstract.py b/aiida/repository/backend/abstract.py
index 9a3527c97a..20621fb584 100644
--- a/aiida/repository/backend/abstract.py
+++ b/aiida/repository/backend/abstract.py
@@ -10,7 +10,7 @@
 import hashlib
 import io
 import pathlib
-import typing
+from typing import BinaryIO, Iterable, Iterator, List, Optional, Union
 
 from aiida.common.hashing import chunked_file_hash
 
@@ -30,9 +30,19 @@ class AbstractRepositoryBackend(metaclass=abc.ABCMeta):
 
     @property
     @abc.abstractmethod
-    def uuid(self) -> typing.Optional[str]:
+    def uuid(self) -> Optional[str]:
         """Return the unique identifier of the repository."""
 
+    @property
+    @abc.abstractmethod
+    def key_format(self) -> Optional[str]:
+        """Return the format for the keys of the repository.
+
+        Important for when migrating between backends (e.g. archive -> main), as if they are not equal then it is
+        necessary to re-compute all the `Node.repository_metadata` before importing (otherwise they will not match
+        with the repository).
+        """
+
     @abc.abstractmethod
     def initialise(self, **kwargs) -> None:
         """Initialise the repository if it hasn't already been initialised.
@@ -58,7 +68,7 @@ def erase(self) -> None:
     def is_readable_byte_stream(handle) -> bool:
         return hasattr(handle, 'read') and hasattr(handle, 'mode') and 'b' in handle.mode
 
-    def put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
+    def put_object_from_filelike(self, handle: BinaryIO) -> str:
         """Store the byte contents of a file in the repository.
 
         :param handle: filelike object with the byte content to be stored.
@@ -70,10 +80,10 @@ def put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
         return self._put_object_from_filelike(handle)
 
     @abc.abstractmethod
-    def _put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
+    def _put_object_from_filelike(self, handle: BinaryIO) -> str:
         pass
 
-    def put_object_from_file(self, filepath: typing.Union[str, pathlib.Path]) -> str:
+    def put_object_from_file(self, filepath: Union[str, pathlib.Path]) -> str:
         """Store a new object with contents of the file located at `filepath` on this file system.
 
         :param filepath: absolute path of file whose contents to copy to the repository.
@@ -84,15 +94,33 @@ def put_object_from_file(self, filepath: typing.Union[str, pathlib.Path]) -> str
             return self.put_object_from_filelike(handle)
 
     @abc.abstractmethod
+    def has_objects(self, keys: List[str]) -> List[bool]:
+        """Return whether the repository has an object with the given key.
+
+        :param keys:
+            list of fully qualified identifiers for objects within the repository.
+        :return:
+            list of logicals, in the same order as the keys provided, with value True if the respective
+            object exists and False otherwise.
+        """
+
     def has_object(self, key: str) -> bool:
         """Return whether the repository has an object with the given key.
 
         :param key: fully qualified identifier for the object within the repository.
         :return: True if the object exists, False otherwise.
         """
+        return self.has_objects([key])[0]
+
+    @abc.abstractmethod
+    def list_objects(self) -> Iterable[str]:
+        """Return iterable that yields all available objects by key.
+
+        :return: An iterable for all the available object keys.
+        """
 
     @contextlib.contextmanager
-    def open(self, key: str) -> typing.Iterator[typing.BinaryIO]:
+    def open(self, key: str) -> Iterator[BinaryIO]:
         """Open a file handle to an object stored under the given key.
 
         .. note:: this should only be used to open a handle to read an existing file. To write a new file use the method
@@ -130,12 +158,27 @@ def get_object_hash(self, key: str) -> str:
         with self.open(key) as handle:  # pylint: disable=not-context-manager
             return chunked_file_hash(handle, hashlib.sha256)
 
-    def delete_object(self, key: str):
+    @abc.abstractmethod
+    def delete_objects(self, keys: List[str]) -> None:
+        """Delete the objects from the repository.
+
+        :param keys: list of fully qualified identifiers for the objects within the repository.
+        :raise FileNotFoundError: if any of the files does not exist.
+        :raise OSError: if any of the files could not be deleted.
+        """
+        keys_exist = self.has_objects(keys)
+        if not all(keys_exist):
+            error_message = 'some of the keys provided do not correspond to any object in the repository:\n'
+            for indx, key_exists in enumerate(keys_exist):
+                if not key_exists:
+                    error_message += f' > object with key `{keys[indx]}` does not exist.\n'
+            raise FileNotFoundError(error_message)
+
+    def delete_object(self, key: str) -> None:
         """Delete the object from the repository.
 
         :param key: fully qualified identifier for the object within the repository.
         :raise FileNotFoundError: if the file does not exist.
         :raise OSError: if the file could not be deleted.
         """
-        if not self.has_object(key):
-            raise FileNotFoundError(f'object with key `{key}` does not exist.')
+        return self.delete_objects([key])
diff --git a/aiida/repository/backend/disk_object_store.py b/aiida/repository/backend/disk_object_store.py
index c4c5306317..387475aff3 100644
--- a/aiida/repository/backend/disk_object_store.py
+++ b/aiida/repository/backend/disk_object_store.py
@@ -2,7 +2,7 @@
 """Implementation of the ``AbstractRepositoryBackend`` using the ``disk-objectstore`` as the backend."""
 import contextlib
 import shutil
-import typing
+from typing import BinaryIO, Iterable, Iterator, List, Optional
 
 from disk_objectstore import Container
 
@@ -27,12 +27,16 @@ def __str__(self) -> str:
         return 'DiskObjectStoreRepository: <uninitialised>'
 
     @property
-    def uuid(self) -> typing.Optional[str]:
+    def uuid(self) -> Optional[str]:
         """Return the unique identifier of the repository."""
         if not self.is_initialised:
             return None
         return self.container.container_id
 
+    @property
+    def key_format(self) -> Optional[str]:
+        return self.container.hash_type
+
     def initialise(self, **kwargs) -> None:
         """Initialise the repository if it hasn't already been initialised.
 
@@ -56,25 +60,20 @@ def erase(self):
         except FileNotFoundError:
             pass
 
-    def _put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
+    def _put_object_from_filelike(self, handle: BinaryIO) -> str:
         """Store the byte contents of a file in the repository.
 
         :param handle: filelike object with the byte content to be stored.
         :return: the generated fully qualified identifier for the object within the repository.
         :raises TypeError: if the handle is not a byte stream.
         """
-        return self.container.add_object(handle.read())
+        return self.container.add_streamed_object(handle)
 
-    def has_object(self, key: str) -> bool:
-        """Return whether the repository has an object with the given key.
-
-        :param key: fully qualified identifier for the object within the repository.
-        :return: True if the object exists, False otherwise.
-        """
-        return self.container.has_object(key)
+    def has_objects(self, keys: List[str]) -> List[bool]:
+        return self.container.has_objects(keys)
 
     @contextlib.contextmanager
-    def open(self, key: str) -> typing.Iterator[typing.BinaryIO]:
+    def open(self, key: str) -> Iterator[BinaryIO]:
         """Open a file handle to an object stored under the given key.
 
         .. note:: this should only be used to open a handle to read an existing file. To write a new file use the method
@@ -90,15 +89,12 @@ def open(self, key: str) -> typing.Iterator[typing.BinaryIO]:
         with self.container.get_object_stream(key) as handle:
             yield handle  # type: ignore[misc]
 
-    def delete_object(self, key: str):
-        """Delete the object from the repository.
+    def delete_objects(self, keys: List[str]) -> None:
+        super().delete_objects(keys)
+        self.container.delete_objects(keys)
 
-        :param key: fully qualified identifier for the object within the repository.
-        :raise FileNotFoundError: if the file does not exist.
-        :raise OSError: if the file could not be deleted.
-        """
-        super().delete_object(key)
-        self.container.delete_objects([key])
+    def list_objects(self) -> Iterable[str]:
+        return self.container.list_all_objects()
 
     def get_object_hash(self, key: str) -> str:
         """Return the SHA-256 hash of an object stored under the given key.
diff --git a/aiida/repository/backend/sandbox.py b/aiida/repository/backend/sandbox.py
index f4577f4783..719ff6f7bb 100644
--- a/aiida/repository/backend/sandbox.py
+++ b/aiida/repository/backend/sandbox.py
@@ -3,7 +3,7 @@
 import contextlib
 import os
 import shutil
-import typing
+from typing import BinaryIO, Iterable, Iterator, List, Optional
 import uuid
 
 from .abstract import AbstractRepositoryBackend
@@ -16,7 +16,7 @@ class SandboxRepositoryBackend(AbstractRepositoryBackend):
 
     def __init__(self):
         from aiida.common.folders import SandboxFolder
-        self._sandbox: typing.Optional[SandboxFolder] = None
+        self._sandbox: Optional[SandboxFolder] = None
 
     def __str__(self) -> str:
         """Return the string representation of this repository."""
@@ -29,13 +29,17 @@ def __del__(self):
         self.erase()
 
     @property
-    def uuid(self) -> typing.Optional[str]:
+    def uuid(self) -> Optional[str]:
         """Return the unique identifier of the repository.
 
         .. note:: A sandbox folder does not have the concept of a unique identifier and so always returns ``None``.
         """
         return None
 
+    @property
+    def key_format(self) -> Optional[str]:
+        return 'uuid4'
+
     def initialise(self, **kwargs) -> None:
         """Initialise the repository if it hasn't already been initialised.
 
@@ -70,7 +74,7 @@ def erase(self):
             finally:
                 self._sandbox = None
 
-    def _put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
+    def _put_object_from_filelike(self, handle: BinaryIO) -> str:
         """Store the byte contents of a file in the repository.
 
         :param handle: filelike object with the byte content to be stored.
@@ -85,16 +89,15 @@ def _put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
 
         return key
 
-    def has_object(self, key: str) -> bool:
-        """Return whether the repository has an object with the given key.
-
-        :param key: fully qualified identifier for the object within the repository.
-        :return: True if the object exists, False otherwise.
-        """
-        return key in os.listdir(self.sandbox.abspath)
+    def has_objects(self, keys: List[str]) -> List[bool]:
+        result = list()
+        dirlist = os.listdir(self.sandbox.abspath)
+        for key in keys:
+            result.append(key in dirlist)
+        return result
 
     @contextlib.contextmanager
-    def open(self, key: str) -> typing.Iterator[typing.BinaryIO]:
+    def open(self, key: str) -> Iterator[BinaryIO]:
         """Open a file handle to an object stored under the given key.
 
         .. note:: this should only be used to open a handle to read an existing file. To write a new file use the method
@@ -110,12 +113,10 @@ def open(self, key: str) -> typing.Iterator[typing.BinaryIO]:
         with self.sandbox.open(key, mode='rb') as handle:
             yield handle
 
-    def delete_object(self, key: str):
-        """Delete the object from the repository.
+    def delete_objects(self, keys: List[str]) -> None:
+        super().delete_objects(keys)
+        for key in keys:
+            os.remove(os.path.join(self.sandbox.abspath, key))
 
-        :param key: fully qualified identifier for the object within the repository.
-        :raise FileNotFoundError: if the file does not exist.
-        :raise OSError: if the file could not be deleted.
-        """
-        super().delete_object(key)
-        os.remove(os.path.join(self.sandbox.abspath, key))
+    def list_objects(self) -> Iterable[str]:
+        return self.sandbox.get_content_list()
diff --git a/tests/repository/backend/test_abstract.py b/tests/repository/backend/test_abstract.py
index 3a548bd515..293d40fc61 100644
--- a/tests/repository/backend/test_abstract.py
+++ b/tests/repository/backend/test_abstract.py
@@ -3,7 +3,7 @@
 """Tests for the :mod:`aiida.repository.backend.abstract` module."""
 import io
 import tempfile
-import typing
+from typing import BinaryIO, Iterable, List, Optional
 
 import pytest
 
@@ -13,11 +13,12 @@
 class RepositoryBackend(AbstractRepositoryBackend):
     """Concrete implementation of ``AbstractRepositoryBackend``."""
 
-    def has_object(self, key):
-        return True
+    @property
+    def uuid(self) -> Optional[str]:
+        return None
 
     @property
-    def uuid(self) -> typing.Optional[str]:
+    def key_format(self) -> Optional[str]:
         return None
 
     def initialise(self, **kwargs) -> None:
@@ -30,7 +31,19 @@ def erase(self):
     def is_initialised(self) -> bool:
         return True
 
-    def _put_object_from_filelike(self, handle: typing.BinaryIO) -> str:
+    def _put_object_from_filelike(self, handle: BinaryIO) -> str:
+        pass
+
+    # pylint useless-super-delegation needs to be disabled here because it refuses to
+    # recognize that this is an abstract method and thus has to be overriden. See the
+    # following issue: https://github.com/PyCQA/pylint/issues/1594
+    def delete_objects(self, keys: List[str]) -> None:  # pylint: disable=useless-super-delegation
+        super().delete_objects(keys)
+
+    def has_objects(self, keys: List[str]) -> List[bool]:
+        return [True]
+
+    def list_objects(self) -> Iterable[str]:
         pass
 
 
@@ -84,3 +97,35 @@ def test_put_object_from_file(repository, generate_directory):
 
     repository.put_object_from_file(directory / 'file_a')
     repository.put_object_from_file(str(directory / 'file_a'))
+
+
+def test_passes_to_batch(repository, monkeypatch):
+    """Checks that the single object operations call the batch operations"""
+
+    def mock_batch_operation(self, keys):
+        raise NotImplementedError('this method was intentionally not implemented')
+
+    monkeypatch.setattr(RepositoryBackend, 'has_objects', mock_batch_operation)
+    with pytest.raises(NotImplementedError) as execinfo:
+        repository.has_object('object_key')
+    assert str(execinfo.value) == 'this method was intentionally not implemented'
+
+    monkeypatch.undo()
+
+    monkeypatch.setattr(RepositoryBackend, 'delete_objects', mock_batch_operation)
+    with pytest.raises(NotImplementedError) as execinfo:
+        repository.delete_object('object_key')
+    assert str(execinfo.value) == 'this method was intentionally not implemented'
+
+
+def test_delete_objects_test(repository, monkeypatch):
+    """Checks that the super of delete_objects will check for existence of the files"""
+
+    def has_objects_mock(self, keys):  # pylint: disable=unused-argument
+        return [False for key in keys]
+
+    monkeypatch.setattr(RepositoryBackend, 'has_objects', has_objects_mock)
+    with pytest.raises(FileNotFoundError) as execinfo:
+        repository.delete_objects(['object_key'])
+    assert 'exist' in str(execinfo.value)
+    assert 'object_key' in str(execinfo.value)
diff --git a/tests/repository/backend/test_disk_object_store.py b/tests/repository/backend/test_disk_object_store.py
index 8d668fb0ce..4d3b943d4c 100644
--- a/tests/repository/backend/test_disk_object_store.py
+++ b/tests/repository/backend/test_disk_object_store.py
@@ -152,3 +152,25 @@ def test_get_object_hash(repository, generate_directory):
         key = repository.put_object_from_filelike(handle)
 
     assert repository.get_object_hash(key) == 'ed7002b439e9ac845f22357d822bac1444730fbdb6016d3ec9432297b9ec9f73'
+
+
+def test_list_objects(repository, generate_directory):
+    """Test the ``Repository.delete_object`` method."""
+    repository.initialise()
+    keylist = list()
+
+    directory = generate_directory({'file_a': b'content a'})
+    with open(directory / 'file_a', 'rb') as handle:
+        keylist.append(repository.put_object_from_filelike(handle))
+
+    directory = generate_directory({'file_b': b'content b'})
+    with open(directory / 'file_b', 'rb') as handle:
+        keylist.append(repository.put_object_from_filelike(handle))
+
+    assert sorted(list(repository.list_objects())) == sorted(keylist)
+
+
+def test_key_format(repository):
+    """Test the ``key_format`` property."""
+    repository.initialise()
+    assert repository.key_format == repository.container.hash_type
diff --git a/tests/repository/backend/test_sandbox.py b/tests/repository/backend/test_sandbox.py
index 3ef0694c5b..6828c58549 100644
--- a/tests/repository/backend/test_sandbox.py
+++ b/tests/repository/backend/test_sandbox.py
@@ -152,3 +152,25 @@ def test_get_object_hash(repository, generate_directory):
         key = repository.put_object_from_filelike(handle)
 
     assert repository.get_object_hash(key) == 'ed7002b439e9ac845f22357d822bac1444730fbdb6016d3ec9432297b9ec9f73'
+
+
+def test_list_objects(repository, generate_directory):
+    """Test the ``Repository.delete_object`` method."""
+    repository.initialise()
+    keylist = list()
+
+    directory = generate_directory({'file_a': b'content a'})
+    with open(directory / 'file_a', 'rb') as handle:
+        keylist.append(repository.put_object_from_filelike(handle))
+
+    directory = generate_directory({'file_b': b'content b'})
+    with open(directory / 'file_b', 'rb') as handle:
+        keylist.append(repository.put_object_from_filelike(handle))
+
+    assert sorted(list(repository.list_objects())) == sorted(keylist)
+
+
+def test_key_format(repository):
+    """Test the ``key_format`` property."""
+    repository.initialise()
+    assert repository.key_format == 'uuid4'