diff --git a/addons/survey/models/survey_question.py b/addons/survey/models/survey_question.py
index c1e11f1d7d9..b2dfe4fa5e9 100644
--- a/addons/survey/models/survey_question.py
+++ b/addons/survey/models/survey_question.py
@@ -705,8 +705,8 @@ class SurveyQuestionAnswer(models.Model):
     MAX_ANSWER_NAME_LENGTH = 90  # empirically tested in client dropdown
 
     # question and question related fields
-    question_id = fields.Many2one('survey.question', string='Question', ondelete='cascade')
-    matrix_question_id = fields.Many2one('survey.question', string='Question (as matrix row)', ondelete='cascade')
+    question_id = fields.Many2one('survey.question', string='Question', ondelete='cascade', index='btree_not_null')
+    matrix_question_id = fields.Many2one('survey.question', string='Question (as matrix row)', ondelete='cascade', index='btree_not_null')
     question_type = fields.Selection(related='question_id.question_type')
     sequence = fields.Integer('Label Sequence order', default=10)
     scoring_type = fields.Selection(related='question_id.scoring_type')
diff --git a/addons/survey/models/survey_user_input.py b/addons/survey/models/survey_user_input.py
index 8ca8a4a9ffb..11e252510b9 100644
--- a/addons/survey/models/survey_user_input.py
+++ b/addons/survey/models/survey_user_input.py
@@ -23,7 +23,7 @@ class SurveyUserInput(models.Model):
     _inherit = ['mail.thread', 'mail.activity.mixin']
 
     # answer description
-    survey_id = fields.Many2one('survey.survey', string='Survey', required=True, readonly=True, ondelete='cascade')
+    survey_id = fields.Many2one('survey.survey', string='Survey', required=True, readonly=True, ondelete='cascade', index=True)
     scoring_type = fields.Selection(string="Scoring", related="survey_id.scoring_type")
     start_datetime = fields.Datetime('Start date and time', readonly=True)
     end_datetime = fields.Datetime('End date and time', readonly=True)
@@ -43,7 +43,7 @@ class SurveyUserInput(models.Model):
     # identification / access
     access_token = fields.Char('Identification token', default=lambda self: str(uuid.uuid4()), readonly=True, required=True, copy=False)
     invite_token = fields.Char('Invite token', readonly=True, copy=False)  # no unique constraint, as it identifies a pool of attempts
-    partner_id = fields.Many2one('res.partner', string='Contact', readonly=True)
+    partner_id = fields.Many2one('res.partner', string='Contact', readonly=True, index='btree_not_null')
     email = fields.Char('Email', readonly=True)
     nickname = fields.Char('Nickname', help="Attendee nickname, mainly used to identify them in the survey session leaderboard.")
     # questions / answers
@@ -708,7 +708,7 @@ class SurveyUserInputLine(models.Model):
     # survey data
     user_input_id = fields.Many2one('survey.user_input', string='User Input', ondelete='cascade', required=True, index=True)
     survey_id = fields.Many2one(related='user_input_id.survey_id', string='Survey', store=True, readonly=False)
-    question_id = fields.Many2one('survey.question', string='Question', ondelete='cascade', required=True)
+    question_id = fields.Many2one('survey.question', string='Question', ondelete='cascade', required=True, index=True)
     page_id = fields.Many2one(related='question_id.page_id', string="Section", readonly=False)
     question_sequence = fields.Integer('Sequence', related='question_id.sequence', store=True)
     # answer