diff --git a/canaille/app/forms.py b/canaille/app/forms.py
index 6f40a7f5..ed8605c6 100644
--- a/canaille/app/forms.py
+++ b/canaille/app/forms.py
@@ -15,6 +15,7 @@ from canaille.app.i18n import DEFAULT_LANGUAGE_CODE
 from canaille.app.i18n import gettext as _
 from canaille.app.i18n import locale_selector
 from canaille.app.i18n import timezone_selector
+from canaille.backends import BaseBackend
 
 from . import validate_uri
 from .flask import request_is_htmx
@@ -188,7 +189,7 @@ class TableForm(I18NFormMixin, FlaskForm):
         if self.query.data:
             self.items = cls.fuzzy(self.query.data, fields, **filter)
         else:
-            self.items = cls.query(**filter)
+            self.items = BaseBackend.get().query(cls, **filter)
 
         self.page_size = page_size
         self.nb_items = len(self.items)
diff --git a/canaille/backends/__init__.py b/canaille/backends/__init__.py
index 93908f34..0a3ef313 100644
--- a/canaille/backends/__init__.py
+++ b/canaille/backends/__init__.py
@@ -54,6 +54,25 @@ class BaseBackend:
         """
         raise NotImplementedError()
 
+    def query(self, model, **kwargs):
+        """
+        Perform a query on the database and return a collection of instances.
+        Parameters can be any valid attribute with the expected value:
+
+        >>> backend.query(User, first_name="George")
+
+        If several arguments are passed, the methods only returns the model
+        instances that return matches all the argument values:
+
+        >>> backend.query(User, first_name="George", last_name="Abitbol")
+
+        If the argument value is a collection, the methods will return the
+        models that matches any of the values:
+
+        >>> backend.query(User, first_name=["George", "Jane"])
+        """
+        raise NotImplementedError()
+
     def check_user_password(self, user, password: str) -> bool:
         """Check if the password matches the user password in the database."""
         raise NotImplementedError()
diff --git a/canaille/backends/ldap/backend.py b/canaille/backends/ldap/backend.py
index b25050ae..8486808a 100644
--- a/canaille/backends/ldap/backend.py
+++ b/canaille/backends/ldap/backend.py
@@ -16,6 +16,7 @@ from canaille.app.i18n import gettext as _
 from canaille.backends import BaseBackend
 
 from .utils import listify
+from .utils import python_attrs_to_ldap
 
 
 @contextmanager
@@ -243,13 +244,64 @@ class Backend(BaseBackend):
         return result, message
 
     def set_user_password(self, user, password):
-        conn = Backend.get().connection
+        conn = self.connection
         conn.passwd_s(
             user.dn,
             None,
             password.encode("utf-8"),
         )
 
+    def query(self, model, dn=None, filter=None, **kwargs):
+        from .ldapobjectquery import LDAPObjectQuery
+
+        base = dn
+        if dn is None:
+            base = f"{model.base},{model.root_dn}"
+        elif "=" not in base:
+            base = ldap.dn.escape_dn_chars(base)
+            base = f"{model.rdn_attribute}={base},{model.base},{model.root_dn}"
+
+        class_filter = (
+            "".join([f"(objectClass={oc})" for oc in model.ldap_object_class])
+            if getattr(model, "ldap_object_class")
+            else ""
+        )
+        if class_filter:
+            class_filter = f"(|{class_filter})"
+
+        arg_filter = ""
+        ldap_args = python_attrs_to_ldap(
+            {
+                model.python_attribute_to_ldap(name): values
+                for name, values in kwargs.items()
+                if values is not None
+            },
+            encode=False,
+        )
+        for key, value in ldap_args.items():
+            if len(value) == 1:
+                escaped_value = ldap.filter.escape_filter_chars(value[0])
+                arg_filter += f"({key}={escaped_value})"
+
+            else:
+                values = [ldap.filter.escape_filter_chars(v) for v in value]
+                arg_filter += (
+                    "(|" + "".join([f"({key}={value})" for value in values]) + ")"
+                )
+
+        if not filter:
+            filter = ""
+
+        ldapfilter = f"(&{class_filter}{arg_filter}{filter})"
+        base = base or f"{model.base},{model.root_dn}"
+        try:
+            result = self.connection.search_s(
+                base, ldap.SCOPE_SUBTREE, ldapfilter or None, ["+", "*"]
+            )
+        except ldap.NO_SUCH_OBJECT:
+            result = []
+        return LDAPObjectQuery(model, result)
+
 
 def setup_ldap_models(config):
     from canaille.app import models
diff --git a/canaille/backends/ldap/ldapobject.py b/canaille/backends/ldap/ldapobject.py
index fbd091ad..df41fabe 100644
--- a/canaille/backends/ldap/ldapobject.py
+++ b/canaille/backends/ldap/ldapobject.py
@@ -4,42 +4,15 @@ import ldap.dn
 import ldap.filter
 from ldap.controls.readentry import PostReadControl
 
+from canaille.backends import BaseBackend
 from canaille.backends.models import BackendModel
 
 from .backend import Backend
-from .ldapobjectquery import LDAPObjectQuery
+from .utils import attribute_ldap_syntax
 from .utils import cardinalize_attribute
 from .utils import ldap_to_python
 from .utils import listify
-from .utils import python_to_ldap
-
-
-def python_attrs_to_ldap(attrs, encode=True, null_allowed=True):
-    formatted_attrs = {
-        name: [
-            python_to_ldap(value, attribute_ldap_syntax(name), encode=encode)
-            for value in listify(values)
-        ]
-        for name, values in attrs.items()
-    }
-    if not null_allowed:
-        formatted_attrs = {
-            key: [value for value in values if value]
-            for key, values in formatted_attrs.items()
-            if values
-        }
-    return formatted_attrs
-
-
-def attribute_ldap_syntax(attribute_name):
-    ldap_attrs = LDAPObject.ldap_object_attributes()
-    if attribute_name not in ldap_attrs:
-        return None
-
-    if ldap_attrs[attribute_name].syntax:
-        return ldap_attrs[attribute_name].syntax
-
-    return attribute_ldap_syntax(ldap_attrs[attribute_name].sup[0])
+from .utils import python_attrs_to_ldap
 
 
 class LDAPObjectMetaclass(type):
@@ -256,7 +229,7 @@ class LDAPObject(BackendModel, metaclass=LDAPObjectMetaclass):
     @classmethod
     def get(cls, identifier=None, /, **kwargs):
         try:
-            return cls.query(identifier, **kwargs)[0]
+            return BaseBackend.get().query(cls, identifier, **kwargs)[0]
         except (IndexError, ldap.NO_SUCH_OBJECT):
             if identifier and cls.base:
                 return (
@@ -267,58 +240,6 @@ class LDAPObject(BackendModel, metaclass=LDAPObjectMetaclass):
 
             return None
 
-    @classmethod
-    def query(cls, dn=None, filter=None, **kwargs):
-        conn = Backend.get().connection
-
-        base = dn
-        if dn is None:
-            base = f"{cls.base},{cls.root_dn}"
-        elif "=" not in base:
-            base = ldap.dn.escape_dn_chars(base)
-            base = f"{cls.rdn_attribute}={base},{cls.base},{cls.root_dn}"
-
-        class_filter = (
-            "".join([f"(objectClass={oc})" for oc in cls.ldap_object_class])
-            if getattr(cls, "ldap_object_class")
-            else ""
-        )
-        if class_filter:
-            class_filter = f"(|{class_filter})"
-
-        arg_filter = ""
-        ldap_args = python_attrs_to_ldap(
-            {
-                cls.python_attribute_to_ldap(name): values
-                for name, values in kwargs.items()
-                if values is not None
-            },
-            encode=False,
-        )
-        for key, value in ldap_args.items():
-            if len(value) == 1:
-                escaped_value = ldap.filter.escape_filter_chars(value[0])
-                arg_filter += f"({key}={escaped_value})"
-
-            else:
-                values = [ldap.filter.escape_filter_chars(v) for v in value]
-                arg_filter += (
-                    "(|" + "".join([f"({key}={value})" for value in values]) + ")"
-                )
-
-        if not filter:
-            filter = ""
-
-        ldapfilter = f"(&{class_filter}{arg_filter}{filter})"
-        base = base or f"{cls.base},{cls.root_dn}"
-        try:
-            result = conn.search_s(
-                base, ldap.SCOPE_SUBTREE, ldapfilter or None, ["+", "*"]
-            )
-        except ldap.NO_SUCH_OBJECT:
-            result = []
-        return LDAPObjectQuery(cls, result)
-
     @classmethod
     def fuzzy(cls, query, attributes=None, **kwargs):
         query = ldap.filter.escape_filter_chars(query)
@@ -327,7 +248,7 @@ class LDAPObject(BackendModel, metaclass=LDAPObjectMetaclass):
         filter = (
             "(|" + "".join(f"({attribute}=*{query}*)" for attribute in attributes) + ")"
         )
-        return cls.query(filter=filter, **kwargs)
+        return BaseBackend.get().query(cls, filter=filter, **kwargs)
 
     @classmethod
     def update_ldap_attributes(cls):
diff --git a/canaille/backends/ldap/utils.py b/canaille/backends/ldap/utils.py
index a21a4375..63186976 100644
--- a/canaille/backends/ldap/utils.py
+++ b/canaille/backends/ldap/utils.py
@@ -95,3 +95,33 @@ def cardinalize_attribute(python_unique, value):
         return value[0]
 
     return [v for v in value if v is not None]
+
+
+def python_attrs_to_ldap(attrs, encode=True, null_allowed=True):
+    formatted_attrs = {
+        name: [
+            python_to_ldap(value, attribute_ldap_syntax(name), encode=encode)
+            for value in listify(values)
+        ]
+        for name, values in attrs.items()
+    }
+    if not null_allowed:
+        formatted_attrs = {
+            key: [value for value in values if value]
+            for key, values in formatted_attrs.items()
+            if values
+        }
+    return formatted_attrs
+
+
+def attribute_ldap_syntax(attribute_name):
+    from .ldapobject import LDAPObject
+
+    ldap_attrs = LDAPObject.ldap_object_attributes()
+    if attribute_name not in ldap_attrs:
+        return None
+
+    if ldap_attrs[attribute_name].syntax:
+        return ldap_attrs[attribute_name].syntax
+
+    return attribute_ldap_syntax(ldap_attrs[attribute_name].sup[0])
diff --git a/canaille/backends/memory/backend.py b/canaille/backends/memory/backend.py
index c0662094..0ba676d9 100644
--- a/canaille/backends/memory/backend.py
+++ b/canaille/backends/memory/backend.py
@@ -40,3 +40,28 @@ class Backend(BaseBackend):
     def set_user_password(self, user, password):
         user.password = password
         user.save()
+
+    def query(self, model, **kwargs):
+        # if there is no filter, return all models
+        if not kwargs:
+            states = model.index().values()
+            return [model(**state) for state in states]
+
+        # get the ids from the attribute indexes
+        ids = {
+            id
+            for attribute, values in kwargs.items()
+            for value in model.serialize(model.listify(values))
+            for id in model.attribute_index(attribute).get(value, [])
+        }
+
+        # get the states from the ids
+        states = [model.index()[id] for id in ids]
+
+        # initialize instances from the states
+        instances = [model(**state) for state in states]
+        for instance in instances:
+            # TODO: maybe find a way to not initialize the cache in the first place?
+            instance._cache = {}
+
+        return instances
diff --git a/canaille/backends/memory/models.py b/canaille/backends/memory/models.py
index 8c9317d0..ac772821 100644
--- a/canaille/backends/memory/models.py
+++ b/canaille/backends/memory/models.py
@@ -6,6 +6,7 @@ import uuid
 import canaille.core.models
 import canaille.oidc.models
 from canaille.app import models
+from canaille.backends import BaseBackend
 from canaille.backends.models import BackendModel
 
 
@@ -25,31 +26,6 @@ class MemoryModel(BackendModel):
     def __repr__(self):
         return f"<{self.__class__.__name__} id={self.id}>"
 
-    @classmethod
-    def query(cls, **kwargs):
-        # if there is no filter, return all models
-        if not kwargs:
-            states = cls.index().values()
-            return [cls(**state) for state in states]
-
-        # get the ids from the attribute indexes
-        ids = {
-            id
-            for attribute, values in kwargs.items()
-            for value in cls.serialize(cls.listify(values))
-            for id in cls.attribute_index(attribute).get(value, [])
-        }
-
-        # get the states from the ids
-        states = [cls.index()[id] for id in ids]
-
-        # initialize instances from the states
-        instances = [cls(**state) for state in states]
-        for instance in instances:
-            # TODO: maybe find a way to not initialize the cache in the first place?
-            instance._cache = {}
-        return instances
-
     @classmethod
     def index(cls, class_name=None):
         return MemoryModel.indexes.setdefault(class_name or cls.__name__, {})
@@ -63,7 +39,7 @@ class MemoryModel(BackendModel):
     @classmethod
     def fuzzy(cls, query, attributes=None, **kwargs):
         attributes = attributes or cls.attributes
-        instances = cls.query(**kwargs)
+        instances = BaseBackend.get().query(cls, **kwargs)
 
         return [
             instance
@@ -85,7 +61,7 @@ class MemoryModel(BackendModel):
                 or None
             )
 
-        results = cls.query(**kwargs)
+        results = BaseBackend.get().query(cls, **kwargs)
         return results[0] if results else None
 
     @classmethod
diff --git a/canaille/backends/models.py b/canaille/backends/models.py
index c115dd3c..c3237e77 100644
--- a/canaille/backends/models.py
+++ b/canaille/backends/models.py
@@ -87,37 +87,16 @@ class BackendModel:
     implemented for every model and for every backend.
     """
 
-    @classmethod
-    def query(cls, **kwargs):
-        """Perform a query on the database and return a collection of
-        instances.
-
-        Parameters can be any valid attribute with the expected value:
-
-        >>> User.query(first_name="George")
-
-        If several arguments are passed, the methods only returns the model
-        instances that return matches all the argument values:
-
-        >>> User.query(first_name="George", last_name="Abitbol")
-
-        If the argument value is a collection, the methods will return the
-        models that matches any of the values:
-
-        >>> User.query(first_name=["George", "Jane"])
-        """
-        raise NotImplementedError()
-
     @classmethod
     def fuzzy(cls, query, attributes=None, **kwargs):
-        """Works like :meth:`~canaille.backends.models.BackendModel.query` but
+        """Works like :meth:`~canaille.backends.BaseBackend.query` but
         attribute values loosely be matched."""
         raise NotImplementedError()
 
     @classmethod
     def get(cls, identifier=None, **kwargs):
-        """Works like :meth:`~canaille.backends.models.BackendModel.query` but
-        return only one element or :py:data:`None` if no item is matching."""
+        """Works like :meth:`~canaille.backends.BaseBackend.query` but return
+        only one element or :py:data:`None` if no item is matching."""
         raise NotImplementedError()
 
     def save(self):
diff --git a/canaille/backends/sql/backend.py b/canaille/backends/sql/backend.py
index adf9e415..310d9200 100644
--- a/canaille/backends/sql/backend.py
+++ b/canaille/backends/sql/backend.py
@@ -1,4 +1,5 @@
 from sqlalchemy import create_engine
+from sqlalchemy import select
 from sqlalchemy.orm import Session
 from sqlalchemy.orm import declarative_base
 
@@ -65,3 +66,15 @@ class Backend(BaseBackend):
     def set_user_password(self, user, password):
         user.password = password
         user.save()
+
+    def query(self, model, **kwargs):
+        filter = [
+            model.attribute_filter(attribute_name, expected_value)
+            for attribute_name, expected_value in kwargs.items()
+        ]
+        return (
+            Backend.get()
+            .db_session.execute(select(model).filter(*filter))
+            .scalars()
+            .all()
+        )
diff --git a/canaille/backends/sql/models.py b/canaille/backends/sql/models.py
index c50a7b5d..5968814e 100644
--- a/canaille/backends/sql/models.py
+++ b/canaille/backends/sql/models.py
@@ -36,19 +36,6 @@ class SqlAlchemyModel(BackendModel):
             f"<{self.__class__.__name__} {self.identifier_attribute}={self.identifier}>"
         )
 
-    @classmethod
-    def query(cls, **kwargs):
-        filter = [
-            cls.attribute_filter(attribute_name, expected_value)
-            for attribute_name, expected_value in kwargs.items()
-        ]
-        return (
-            Backend.get()
-            .db_session.execute(select(cls).filter(*filter))
-            .scalars()
-            .all()
-        )
-
     @classmethod
     def fuzzy(cls, query, attributes=None, **kwargs):
         attributes = attributes or cls.attributes
diff --git a/canaille/core/endpoints/account.py b/canaille/core/endpoints/account.py
index a10bb1e1..d597463f 100644
--- a/canaille/core/endpoints/account.py
+++ b/canaille/core/endpoints/account.py
@@ -86,7 +86,7 @@ def join():
 
     form = JoinForm(request.form or None)
     if request.form and form.validate():
-        if models.User.query(emails=form.email.data):
+        if BaseBackend.get().query(models.User, emails=form.email.data):
             flash(
                 _(
                     "You will receive soon an email to continue the registration process."
@@ -295,7 +295,10 @@ def registration(data=None, hash=None):
     if "groups" not in form and payload and payload.groups:
         form["groups"] = wtforms.SelectMultipleField(
             _("Groups"),
-            choices=[(group, group.display_name) for group in models.Group.query()],
+            choices=[
+                (group, group.display_name)
+                for group in BaseBackend.get().query(models.Group)
+            ],
             coerce=IDToModel("Group"),
         )
         set_readonly(form["groups"])
@@ -388,7 +391,7 @@ def email_confirmation(data, hash):
         )
         return redirect(url_for("core.account.index"))
 
-    if models.User.query(emails=confirmation_obj.email):
+    if BaseBackend.get().query(models.User, emails=confirmation_obj.email):
         flash(
             _("This address email is already associated with another account."),
             "error",
diff --git a/canaille/core/endpoints/forms.py b/canaille/core/endpoints/forms.py
index ad61d59d..375fa78e 100644
--- a/canaille/core/endpoints/forms.py
+++ b/canaille/core/endpoints/forms.py
@@ -312,7 +312,10 @@ PROFILE_FORM_FIELDS = dict(
     groups=wtforms.SelectMultipleField(
         _("Groups"),
         default=[],
-        choices=lambda: [(group, group.display_name) for group in models.Group.query()],
+        choices=lambda: [
+            (group, group.display_name)
+            for group in BaseBackend.get().query(models.Group)
+        ],
         render_kw={"placeholder": _("users, admins …")},
         coerce=IDToModel("Group"),
         validators=[non_empty_groups],
@@ -333,7 +336,7 @@ def build_profile_form(write_field_names, readonly_field_names, user=None):
         if PROFILE_FORM_FIELDS.get(name)
     }
 
-    if "groups" in fields and not models.Group.query():
+    if "groups" in fields and not BaseBackend.get().query(models.Group):
         del fields["groups"]
 
     if current_app.backend.get().has_account_lockability():  # pragma: no branch
@@ -436,7 +439,10 @@ class InvitationForm(Form):
     )
     groups = wtforms.SelectMultipleField(
         _("Groups"),
-        choices=lambda: [(group, group.display_name) for group in models.Group.query()],
+        choices=lambda: [
+            (group, group.display_name)
+            for group in BaseBackend.get().query(models.Group)
+        ],
         render_kw={},
         coerce=IDToModel("Group"),
     )
diff --git a/canaille/core/populate.py b/canaille/core/populate.py
index f7c38f6d..631b8a0e 100644
--- a/canaille/core/populate.py
+++ b/canaille/core/populate.py
@@ -5,6 +5,7 @@ from faker.config import AVAILABLE_LOCALES
 
 from canaille.app import models
 from canaille.app.i18n import available_language_codes
+from canaille.backends import BaseBackend
 
 
 def fake_users(nb=1):
@@ -47,7 +48,7 @@ def fake_users(nb=1):
 
 
 def fake_groups(nb=1, nb_users_max=1):
-    users = models.User.query()
+    users = BaseBackend.get().query(models.User)
     groups = list()
     fake = faker.Faker(["en_US"])
     for _ in range(nb):
diff --git a/canaille/oidc/commands.py b/canaille/oidc/commands.py
index b8285572..f2442cc9 100644
--- a/canaille/oidc/commands.py
+++ b/canaille/oidc/commands.py
@@ -3,6 +3,7 @@ from flask.cli import with_appcontext
 
 from canaille.app import models
 from canaille.app.commands import with_backendcontext
+from canaille.backends import BaseBackend
 
 
 @click.command()
@@ -10,11 +11,11 @@ from canaille.app.commands import with_backendcontext
 @with_backendcontext
 def clean():
     """Remove expired tokens and authorization codes."""
-    for t in models.Token.query():
+    for t in BaseBackend.get().query(models.Token):
         if t.is_expired():
             t.delete()
 
-    for a in models.AuthorizationCode.query():
+    for a in BaseBackend.get().query(models.AuthorizationCode):
         if a.is_expired():
             a.delete()
 
diff --git a/canaille/oidc/endpoints/consents.py b/canaille/oidc/endpoints/consents.py
index 1bf2db3b..f6c42d7f 100644
--- a/canaille/oidc/endpoints/consents.py
+++ b/canaille/oidc/endpoints/consents.py
@@ -10,6 +10,7 @@ from canaille.app import models
 from canaille.app.flask import user_needed
 from canaille.app.i18n import gettext as _
 from canaille.app.themes import render_template
+from canaille.backends import BaseBackend
 
 from ..utils import SCOPE_DETAILS
 
@@ -19,13 +20,13 @@ bp = Blueprint("consents", __name__, url_prefix="/consent")
 @bp.route("/")
 @user_needed()
 def consents(user):
-    consents = models.Consent.query(subject=user)
+    consents = BaseBackend.get().query(models.Consent, subject=user)
     clients = {t.client for t in consents}
 
     nb_consents = len(consents)
     nb_preconsents = sum(
         1
-        for client in models.Client.query()
+        for client in BaseBackend.get().query(models.Client)
         if client.preconsent and client not in clients
     )
 
@@ -43,11 +44,11 @@ def consents(user):
 @bp.route("/pre-consents")
 @user_needed()
 def pre_consents(user):
-    consents = models.Consent.query(subject=user)
+    consents = BaseBackend.get().query(models.Consent, subject=user)
     clients = {t.client for t in consents}
     preconsented = [
         client
-        for client in models.Client.query()
+        for client in BaseBackend.get().query(models.Client)
         if client.preconsent and client not in clients
     ]
 
diff --git a/canaille/oidc/endpoints/forms.py b/canaille/oidc/endpoints/forms.py
index 4de65a36..317fc991 100644
--- a/canaille/oidc/endpoints/forms.py
+++ b/canaille/oidc/endpoints/forms.py
@@ -7,6 +7,7 @@ from canaille.app.forms import email_validator
 from canaille.app.forms import is_uri
 from canaille.app.forms import unique_values
 from canaille.app.i18n import lazy_gettext as _
+from canaille.backends import BaseBackend
 
 
 class AuthorizeForm(Form):
@@ -18,7 +19,10 @@ class LogoutForm(Form):
 
 
 def client_audiences():
-    return [(client, client.client_name) for client in models.Client.query()]
+    return [
+        (client, client.client_name)
+        for client in BaseBackend.get().query(models.Client)
+    ]
 
 
 class ClientAddForm(Form):
diff --git a/canaille/oidc/endpoints/oauth.py b/canaille/oidc/endpoints/oauth.py
index c3bce4b5..36b5e75f 100644
--- a/canaille/oidc/endpoints/oauth.py
+++ b/canaille/oidc/endpoints/oauth.py
@@ -23,6 +23,7 @@ from canaille.app.flask import logout_user
 from canaille.app.flask import set_parameter_in_url_query
 from canaille.app.i18n import gettext as _
 from canaille.app.themes import render_template
+from canaille.backends import BaseBackend
 
 from ..oauth import ClientConfigurationEndpoint
 from ..oauth import ClientRegistrationEndpoint
@@ -109,7 +110,8 @@ def authorize_login(user):
 def authorize_consent(client, user):
     requested_scopes = request.args.get("scope", "").split(" ")
     allowed_scopes = client.get_allowed_scope(requested_scopes).split(" ")
-    consents = models.Consent.query(
+    consents = BaseBackend.get().query(
+        models.Consent,
         client=client,
         subject=user,
     )
diff --git a/canaille/oidc/models.py b/canaille/oidc/models.py
index 0c7a84c0..4e32c5af 100644
--- a/canaille/oidc/models.py
+++ b/canaille/oidc/models.py
@@ -8,6 +8,7 @@ from authlib.oauth2.rfc6749 import TokenMixin
 from authlib.oauth2.rfc6749 import util
 
 from canaille.app import models
+from canaille.backends import BaseBackend
 
 from .basemodels import AuthorizationCode as BaseAuthorizationCode
 from .basemodels import Client as BaseClient
@@ -95,13 +96,13 @@ class Client(BaseClient, ClientMixin):
         return metadata
 
     def delete(self):
-        for consent in models.Consent.query(client=self):
+        for consent in BaseBackend.get().query(models.Consent, client=self):
             consent.delete()
 
-        for code in models.AuthorizationCode.query(client=self):
+        for code in BaseBackend.get().query(models.AuthorizationCode, client=self):
             code.delete()
 
-        for token in models.Token.query(client=self):
+        for token in BaseBackend.get().query(models.Token, client=self):
             token.delete()
 
         super().delete()
@@ -185,7 +186,8 @@ class Consent(BaseConsent):
         self.revokation_date = datetime.datetime.now(datetime.timezone.utc)
         self.save()
 
-        tokens = models.Token.query(
+        tokens = BaseBackend.get().query(
+            models.Token,
             client=self.client,
             subject=self.subject,
         )
diff --git a/canaille/oidc/oauth.py b/canaille/oidc/oauth.py
index b4031ad3..30b57294 100644
--- a/canaille/oidc/oauth.py
+++ b/canaille/oidc/oauth.py
@@ -112,7 +112,9 @@ def openid_configuration():
 
 def exists_nonce(nonce, req):
     client = models.Client.get(id=req.client_id)
-    exists = models.AuthorizationCode.query(client=client, nonce=nonce)
+    exists = BaseBackend.get().query(
+        models.AuthorizationCode, client=client, nonce=nonce
+    )
     return bool(exists)
 
 
@@ -237,7 +239,9 @@ class AuthorizationCodeGrant(_AuthorizationCodeGrant):
         return save_authorization_code(code, request)
 
     def query_authorization_code(self, code, client):
-        item = models.AuthorizationCode.query(code=code, client=client)
+        item = BaseBackend.get().query(
+            models.AuthorizationCode, code=code, client=client
+        )
         if item and not item[0].is_expired():
             return item[0]
 
@@ -283,7 +287,7 @@ class RefreshTokenGrant(_RefreshTokenGrant):
     TOKEN_ENDPOINT_AUTH_METHODS = ["client_secret_basic", "client_secret_post", "none"]
 
     def authenticate_refresh_token(self, refresh_token):
-        token = models.Token.query(refresh_token=refresh_token)
+        token = BaseBackend.get().query(models.Token, refresh_token=refresh_token)
         if token and token[0].is_refresh_token_active():
             return token[0]
 
diff --git a/tests/backends/ldap/test_utils.py b/tests/backends/ldap/test_utils.py
index 83830b75..faec2a55 100644
--- a/tests/backends/ldap/test_utils.py
+++ b/tests/backends/ldap/test_utils.py
@@ -81,15 +81,15 @@ def test_special_chars_in_rdn(testclient, backend):
 
 
 def test_filter(backend, foo_group, bar_group):
-    assert models.Group.query(display_name="foo") == [foo_group]
-    assert models.Group.query(display_name="bar") == [bar_group]
+    assert backend.query(models.Group, display_name="foo") == [foo_group]
+    assert backend.query(models.Group, display_name="bar") == [bar_group]
 
-    assert models.Group.query(display_name="foo") != 3
+    assert backend.query(models.Group, display_name="foo") != 3
 
-    assert models.Group.query(display_name=["foo"]) == [foo_group]
-    assert models.Group.query(display_name=["bar"]) == [bar_group]
+    assert backend.query(models.Group, display_name=["foo"]) == [foo_group]
+    assert backend.query(models.Group, display_name=["bar"]) == [bar_group]
 
-    assert set(models.Group.query(display_name=["foo", "bar"])) == {
+    assert set(backend.query(models.Group, display_name=["foo", "bar"])) == {
         foo_group,
         bar_group,
     }
diff --git a/tests/backends/test_models.py b/tests/backends/test_models.py
index ef8c1e0d..7ca216e0 100644
--- a/tests/backends/test_models.py
+++ b/tests/backends/test_models.py
@@ -36,16 +36,16 @@ def test_model_lifecycle(testclient, backend):
     )
 
     assert not user.id
-    assert not models.User.query()
-    assert not models.User.query(id=user.id)
-    assert not models.User.query(id="invalid")
+    assert not backend.query(models.User)
+    assert not backend.query(models.User, id=user.id)
+    assert not backend.query(models.User, id="invalid")
     assert not models.User.get(id=user.id)
 
     user.save()
 
-    assert models.User.query() == [user]
-    assert models.User.query(id=user.id) == [user]
-    assert not models.User.query(id="invalid")
+    assert backend.query(models.User) == [user]
+    assert backend.query(models.User, id=user.id) == [user]
+    assert not backend.query(models.User, id="invalid")
     assert models.User.get(id=user.id) == user
 
     user.family_name = "new_family_name"
@@ -58,7 +58,7 @@ def test_model_lifecycle(testclient, backend):
 
     user.delete()
 
-    assert not models.User.query(id=user.id)
+    assert not backend.query(models.User, id=user.id)
     assert not models.User.get(id=user.id)
 
     user.delete()
@@ -143,7 +143,7 @@ def test_model_indexation(testclient, backend):
 
 
 def test_fuzzy_unique_attribute(user, moderator, admin, backend):
-    assert set(models.User.query()) == {user, moderator, admin}
+    assert set(backend.query(models.User)) == {user, moderator, admin}
     assert set(models.User.fuzzy("Jack")) == {moderator}
     assert set(models.User.fuzzy("Jack", ["formatted_name"])) == {moderator}
     assert set(models.User.fuzzy("Jack", ["user_name"])) == set()
@@ -157,7 +157,7 @@ def test_fuzzy_unique_attribute(user, moderator, admin, backend):
 
 
 def test_fuzzy_multiple_attribute(user, moderator, admin, backend):
-    assert set(models.User.query()) == {user, moderator, admin}
+    assert set(backend.query(models.User)) == {user, moderator, admin}
     assert set(models.User.fuzzy("jack@doe.com")) == {moderator}
     assert set(models.User.fuzzy("jack@doe.com", ["emails"])) == {moderator}
     assert set(models.User.fuzzy("jack@doe.com", ["formatted_name"])) == set()
@@ -171,8 +171,8 @@ def test_fuzzy_multiple_attribute(user, moderator, admin, backend):
 def test_model_references(testclient, user, foo_group, admin, bar_group, backend):
     assert foo_group.members == [user]
     assert user.groups == [foo_group]
-    assert foo_group in models.Group.query(members=user)
-    assert user in models.User.query(groups=foo_group)
+    assert foo_group in backend.query(models.Group, members=user)
+    assert user in backend.query(models.User, groups=foo_group)
 
     assert user not in bar_group.members
     assert bar_group not in user.groups
diff --git a/tests/core/commands/test_populate.py b/tests/core/commands/test_populate.py
index 26989680..93fad3e5 100644
--- a/tests/core/commands/test_populate.py
+++ b/tests/core/commands/test_populate.py
@@ -6,11 +6,11 @@ from canaille.core.populate import fake_users
 def test_populate_users(testclient, backend):
     runner = testclient.app.test_cli_runner()
 
-    assert len(models.User.query()) == 0
+    assert len(backend.query(models.User)) == 0
     res = runner.invoke(cli, ["populate", "--nb", "10", "users"])
     assert res.exit_code == 0, res.stdout
-    assert len(models.User.query()) == 10
-    for user in models.User.query():
+    assert len(backend.query(models.User)) == 10
+    for user in backend.query(models.User):
         user.delete()
 
 
@@ -18,13 +18,13 @@ def test_populate_groups(testclient, backend):
     fake_users(10)
     runner = testclient.app.test_cli_runner()
 
-    assert len(models.Group.query()) == 0
+    assert len(backend.query(models.Group)) == 0
     res = runner.invoke(cli, ["populate", "--nb", "10", "groups"])
     assert res.exit_code == 0, res.stdout
-    assert len(models.Group.query()) == 10
+    assert len(backend.query(models.Group)) == 10
 
-    for group in models.Group.query():
+    for group in backend.query(models.Group):
         group.delete()
 
-    for user in models.User.query():
+    for user in backend.query(models.User):
         user.delete()
diff --git a/tests/core/test_groups.py b/tests/core/test_groups.py
index c8f24744..f0087d27 100644
--- a/tests/core/test_groups.py
+++ b/tests/core/test_groups.py
@@ -4,7 +4,7 @@ from canaille.core.populate import fake_users
 
 
 def test_no_group(app, backend):
-    assert models.Group.query() == []
+    assert backend.query(models.Group) == []
 
 
 def test_group_list_pagination(testclient, logged_admin, foo_group):
diff --git a/tests/core/test_registration.py b/tests/core/test_registration.py
index b989db4b..7d41ef95 100644
--- a/tests/core/test_registration.py
+++ b/tests/core/test_registration.py
@@ -12,7 +12,7 @@ def test_registration_without_email_validation(testclient, backend, foo_group):
     testclient.app.config["CANAILLE"]["ENABLE_REGISTRATION"] = True
     testclient.app.config["CANAILLE"]["EMAIL_CONFIRMATION"] = False
 
-    assert not models.User.query(user_name="newuser")
+    assert not backend.query(models.User, user_name="newuser")
     res = testclient.get(url_for("core.account.registration"), status=200)
     res.form["user_name"] = "newuser"
     res.form["password1"] = "password"
@@ -60,7 +60,7 @@ def test_registration_with_email_validation(testclient, backend, smtpd, foo_grou
     text_mail = smtpd.messages[0].get_payload()[0].get_payload(decode=True).decode()
     assert registration_url in text_mail
 
-    assert not models.User.query(user_name="newuser")
+    assert not backend.query(models.User, user_name="newuser")
     with time_machine.travel("2020-01-01 02:01:00+00:00", tick=False):
         res = testclient.get(registration_url, status=200)
         res.form["user_name"] = "newuser"
diff --git a/tests/oidc/test_authorization_code_flow.py b/tests/oidc/test_authorization_code_flow.py
index 6b101e7e..b9d5f45d 100644
--- a/tests/oidc/test_authorization_code_flow.py
+++ b/tests/oidc/test_authorization_code_flow.py
@@ -13,8 +13,10 @@ from canaille.app import models
 from . import client_credentials
 
 
-def test_nominal_case(testclient, logged_user, client, keypair, trusted_client):
-    assert not models.Consent.query()
+def test_nominal_case(
+    testclient, logged_user, client, keypair, trusted_client, backend
+):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -43,7 +45,7 @@ def test_nominal_case(testclient, logged_user, client, keypair, trusted_client):
         "phone",
     }
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert set(consents[0].scope) == {
         "openid",
         "profile",
@@ -112,8 +114,10 @@ def test_invalid_client(testclient, logged_user, keypair):
     )
 
 
-def test_redirect_uri(testclient, logged_user, client, keypair, trusted_client):
-    assert not models.Consent.query()
+def test_redirect_uri(
+    testclient, logged_user, client, keypair, trusted_client, backend
+):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -134,7 +138,7 @@ def test_redirect_uri(testclient, logged_user, client, keypair, trusted_client):
     code = params["code"][0]
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
 
     res = testclient.post(
         "/oauth/token",
@@ -157,8 +161,10 @@ def test_redirect_uri(testclient, logged_user, client, keypair, trusted_client):
         consent.delete()
 
 
-def test_preconsented_client(testclient, logged_user, client, keypair, trusted_client):
-    assert not models.Consent.query()
+def test_preconsented_client(
+    testclient, logged_user, client, keypair, trusted_client, backend
+):
+    assert not backend.query(models.Consent)
 
     client.preconsent = True
     client.save()
@@ -180,7 +186,7 @@ def test_preconsented_client(testclient, logged_user, client, keypair, trusted_c
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert not consents
 
     res = testclient.post(
@@ -214,8 +220,8 @@ def test_preconsented_client(testclient, logged_user, client, keypair, trusted_c
     assert res.json["name"] == "John (johnny) Doe"
 
 
-def test_logout_login(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_logout_login(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -254,7 +260,7 @@ def test_logout_login(testclient, logged_user, client):
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
 
     res = testclient.post(
@@ -285,8 +291,8 @@ def test_logout_login(testclient, logged_user, client):
         consent.delete()
 
 
-def test_deny(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_deny(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -305,11 +311,11 @@ def test_deny(testclient, logged_user, client):
     error = params["error"][0]
     assert error == "access_denied"
 
-    assert not models.Consent.query()
+    assert not backend.query(models.Consent)
 
 
-def test_code_challenge(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_code_challenge(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
 
     client.token_endpoint_auth_method = "none"
     client.save()
@@ -338,7 +344,7 @@ def test_code_challenge(testclient, logged_user, client):
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
 
     res = testclient.post(
@@ -373,8 +379,8 @@ def test_code_challenge(testclient, logged_user, client):
         consent.delete()
 
 
-def test_consent_already_given(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_consent_already_given(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -395,7 +401,7 @@ def test_consent_already_given(testclient, logged_user, client):
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
 
     res = testclient.post(
@@ -430,9 +436,9 @@ def test_consent_already_given(testclient, logged_user, client):
 
 
 def test_when_consent_already_given_but_for_a_smaller_scope(
-    testclient, logged_user, client
+    testclient, logged_user, client, backend
 ):
-    assert not models.Consent.query()
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -453,7 +459,7 @@ def test_when_consent_already_given_but_for_a_smaller_scope(
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
     assert "groups" not in consents[0].scope
 
@@ -489,7 +495,7 @@ def test_when_consent_already_given_but_for_a_smaller_scope(
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
     assert "groups" in consents[0].scope
 
@@ -535,8 +541,8 @@ def test_nonce_required_in_oidc_requests(testclient, logged_user, client):
     assert res.json.get("error") == "invalid_request"
 
 
-def test_nonce_not_required_in_oauth_requests(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_nonce_not_required_in_oauth_requests(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
     testclient.app.config["CANAILLE_OIDC"]["REQUIRE_NONCE"] = False
 
     res = testclient.get(
@@ -552,12 +558,12 @@ def test_nonce_not_required_in_oauth_requests(testclient, logged_user, client):
     res = res.form.submit(name="answer", value="accept", status=302)
 
     assert res.location.startswith(client.redirect_uris[0])
-    for consent in models.Consent.query():
+    for consent in backend.query(models.Consent):
         consent.delete()
 
 
-def test_request_scope_too_large(testclient, logged_user, keypair, client):
-    assert not models.Consent.query()
+def test_request_scope_too_large(testclient, logged_user, keypair, client, backend):
+    assert not backend.query(models.Consent)
     client.scope = ["openid", "profile", "groups"]
     client.save()
 
@@ -582,7 +588,7 @@ def test_request_scope_too_large(testclient, logged_user, keypair, client):
         "profile",
     }
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert set(consents[0].scope) == {
         "openid",
         "profile",
diff --git a/tests/oidc/test_consent.py b/tests/oidc/test_consent.py
index fd1f2c19..b4547a3a 100644
--- a/tests/oidc/test_consent.py
+++ b/tests/oidc/test_consent.py
@@ -95,7 +95,7 @@ def test_someone_else_consent_restoration(
 
 
 def test_oidc_authorization_after_revokation(
-    testclient, logged_user, client, keypair, consent
+    testclient, logged_user, client, keypair, consent, backend
 ):
     consent.revoke()
 
@@ -114,7 +114,7 @@ def test_oidc_authorization_after_revokation(
 
     res = res.form.submit(name="answer", value="accept", status=302)
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     consent.reload()
     assert consents[0] == consent
     assert not consent.revoked
diff --git a/tests/oidc/test_forms.py b/tests/oidc/test_forms.py
index ce76aeac..dae00e7e 100644
--- a/tests/oidc/test_forms.py
+++ b/tests/oidc/test_forms.py
@@ -5,8 +5,8 @@ from canaille.app import models
 # forms.
 
 
-def test_fieldlist_add(testclient, logged_admin):
-    assert not models.Client.query()
+def test_fieldlist_add(testclient, logged_admin, backend):
+    assert not backend.query(models.Client)
 
     res = testclient.get("/admin/client/add")
     assert "redirect_uris-1" not in res.form.fields
@@ -23,7 +23,7 @@ def test_fieldlist_add(testclient, logged_admin):
         res.form[k].force_value(v)
 
     res = res.form.submit(status=200, name="fieldlist_add", value="redirect_uris-0")
-    assert not models.Client.query()
+    assert not backend.query(models.Client)
 
     data["redirect_uris-1"] = "https://foo.bar/callback2"
     for k, v in data.items():
@@ -43,8 +43,8 @@ def test_fieldlist_add(testclient, logged_admin):
     client.delete()
 
 
-def test_fieldlist_delete(testclient, logged_admin):
-    assert not models.Client.query()
+def test_fieldlist_delete(testclient, logged_admin, backend):
+    assert not backend.query(models.Client)
     res = testclient.get("/admin/client/add")
 
     data = {
@@ -61,7 +61,7 @@ def test_fieldlist_delete(testclient, logged_admin):
 
     res.form["redirect_uris-1"] = "https://foo.bar/callback2"
     res = res.form.submit(status=200, name="fieldlist_remove", value="redirect_uris-1")
-    assert not models.Client.query()
+    assert not backend.query(models.Client)
     assert "redirect_uris-1" not in res.form.fields
 
     res = res.form.submit(status=302, name="action", value="edit")
@@ -92,8 +92,8 @@ def test_fieldlist_add_invalid_field(testclient, logged_admin):
     testclient.post("/admin/client/add", data, status=400)
 
 
-def test_fieldlist_delete_invalid_field(testclient, logged_admin):
-    assert not models.Client.query()
+def test_fieldlist_delete_invalid_field(testclient, logged_admin, backend):
+    assert not backend.query(models.Client)
     res = testclient.get("/admin/client/add")
 
     data = {
diff --git a/tests/oidc/test_refresh_token.py b/tests/oidc/test_refresh_token.py
index 3e17bd7e..548ecd42 100644
--- a/tests/oidc/test_refresh_token.py
+++ b/tests/oidc/test_refresh_token.py
@@ -7,8 +7,8 @@ from canaille.app import models
 from . import client_credentials
 
 
-def test_refresh_token(testclient, logged_user, client):
-    assert not models.Consent.query()
+def test_refresh_token(testclient, logged_user, client, backend):
+    assert not backend.query(models.Consent)
 
     res = testclient.get(
         "/oauth/authorize",
@@ -27,7 +27,7 @@ def test_refresh_token(testclient, logged_user, client):
     authcode = models.AuthorizationCode.get(code=code)
     assert authcode is not None
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     assert "profile" in consents[0].scope
 
     res = testclient.post(
diff --git a/tests/oidc/test_token_expiration.py b/tests/oidc/test_token_expiration.py
index b92b7afe..d4883dcd 100644
--- a/tests/oidc/test_token_expiration.py
+++ b/tests/oidc/test_token_expiration.py
@@ -9,7 +9,9 @@ from canaille.oidc.oauth import setup_oauth
 from . import client_credentials
 
 
-def test_token_default_expiration_date(testclient, logged_user, client, keypair):
+def test_token_default_expiration_date(
+    testclient, logged_user, client, keypair, backend
+):
     res = testclient.get(
         "/oauth/authorize",
         params=dict(
@@ -52,12 +54,14 @@ def test_token_default_expiration_date(testclient, logged_user, client, keypair)
     claims = jwt.decode(id_token, keypair[1])
     assert claims["exp"] - claims["iat"] == 3600
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     for consent in consents:
         consent.delete()
 
 
-def test_token_custom_expiration_date(testclient, logged_user, client, keypair):
+def test_token_custom_expiration_date(
+    testclient, logged_user, client, keypair, backend
+):
     testclient.app.config["OAUTH2_TOKEN_EXPIRES_IN"] = {
         "authorization_code": 1000,
         "implicit": 2000,
@@ -110,6 +114,6 @@ def test_token_custom_expiration_date(testclient, logged_user, client, keypair):
     claims = jwt.decode(id_token, keypair[1])
     assert claims["exp"] - claims["iat"] == 6000
 
-    consents = models.Consent.query(client=client, subject=logged_user)
+    consents = backend.query(models.Consent, client=client, subject=logged_user)
     for consent in consents:
         consent.delete()