diff --git a/lib/charms/data_platform_libs/v1/data_interfaces.py b/lib/charms/data_platform_libs/v1/data_interfaces.py
index 0d156cd4..199b7bb6 100644
--- a/lib/charms/data_platform_libs/v1/data_interfaces.py
+++ b/lib/charms/data_platform_libs/v1/data_interfaces.py
@@ -312,7 +312,7 @@ def _on_resource_requested(self, event: ResourceRequestedEvent) -> None:
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 3
+LIBPATCH = 4
 
 PYDEPS = ["ops>=2.0.0", "pydantic>=2.11"]
 
@@ -496,6 +496,9 @@ def store_new_data(
 MtlsSecretStr = Annotated[OptionalSecretStr, Field(exclude=True, default=None), "mtls"]
 ExtraSecretStr = Annotated[OptionalSecretStr, Field(exclude=True, default=None), "extra"]
 EntitySecretStr = Annotated[OptionalSecretStr, Field(exclude=True, default=None), "entity"]
+RequestedEntitySecretStr = Annotated[
+    OptionalSecretStr, Field(exclude=True, default=None), "requested-entity"
+]
 
 
 class Scope(Enum):
@@ -833,9 +836,16 @@ def extract_secrets(self, info: ValidationInfo):
                 if not secret_uri:
                     continue
 
-                secret = repository.get_secret(
-                    secret_group, secret_uri=secret_uri, short_uuid=short_uuid
-                )
+                try:
+                    secret = repository.get_secret(
+                        secret_group, secret_uri=secret_uri, short_uuid=short_uuid
+                    )
+                except SecretNotFoundError:
+                    # v0 deletes the requested entity secret
+                    if secret_group == "requested-entity":
+                        logger.debug("Missing requested entity secret")
+                        continue
+                    raise
 
                 if not secret:
                     logger.info(f"No secret for group {secret_group} and short uuid {short_uuid}")
@@ -1002,6 +1012,13 @@ class RequirerCommonModel(CommonModel):
     entity_permissions: list[EntityPermissionModel] | None = Field(default=None)
     secret_mtls: SecretString | None = Field(default=None)
     mtls_cert: MtlsSecretStr = Field(default=None)
+    secret_requested_entity: SecretString | None = Field(
+        default=None,
+        validation_alias=AliasChoices("requested-entity-secret", "secret-requested-entity"),
+    )
+    entity_name: RequestedEntitySecretStr = Field(default=None)
+    entity_password: RequestedEntitySecretStr = Field(default=None, serialization_alias="password")
+    prefix_matching: Literal["all", "only-existing"] | None = Field(default=None)
 
     @model_validator(mode="after")
     def validate_fields(self):
@@ -1015,6 +1032,9 @@ def validate_fields(self):
         if self.entity_type == "GROUP" and self.extra_user_roles:
             raise ValueError("Inconsistent entity information. Use extra_group_roles instead")
 
+        if self.entity_password and not self.entity_name:
+            raise ValueError("Unable to set entity password without an entity name")
+
         return self
 
 
@@ -1047,6 +1067,7 @@ class ResourceProviderModel(ProviderCommonModel):
     entity_name: EntitySecretStr = Field(default=None)
     entity_password: EntitySecretStr = Field(default=None)
     version: str | None = Field(default=None)
+    prefix_resources: str | None = Field(default=None)
 
 
 class RequirerDataContractV0(RequirerCommonModel):
@@ -2090,6 +2111,12 @@ class AuthenticationUpdatedEvent(ResourceRequirerEvent[TResourceProviderModel]):
     pass
 
 
+class ResourcePrefixResourcesChangedEvent(ResourceRequirerEvent[TResourceProviderModel]):
+    """Prefix resources have changed."""
+
+    pass
+
+
 # Error Propagation Events
 
 
@@ -2148,6 +2175,7 @@ class ResourceRequiresEvents(CharmEvents, Generic[TResourceProviderModel]):
     authentication_updated = EventSource(AuthenticationUpdatedEvent)
     status_raised = EventSource(StatusRaisedEvent)
     status_resolved = EventSource(StatusResolvedEvent)
+    prefix_resources_changed = EventSource(ResourcePrefixResourcesChangedEvent)
 
 
 ##############################################################################
@@ -2632,6 +2660,11 @@ def set_response(self, relation_id: int, response: ResourceProviderModel):
             self.interface.write_model(
                 relation_id, response, context={"version": "v0"}
             )  # {"database": "database-name", "secret-user": "uri", ...}
+            # Set expected prefix field if present
+            if response.prefix_resources:
+                self.interface.repository(relation_id).write_field(
+                    "prefix-databases", response.prefix_resources
+                )
             return
 
         model = self.interface.build_model(relation_id, DataContractV1[response.__class__])
@@ -2875,6 +2908,10 @@ def __init__(
                     f"{relation_alias}_read_only_endpoints_changed",
                     ResourceReadOnlyEndpointsChangedEvent,
                 )
+                self.on.define_event(
+                    f"{relation_alias}_prefix_resources_changed",
+                    ResourcePrefixResourcesChangedEvent,
+                )
 
     ##############################################################################
     # Extra useful functions
@@ -3241,3 +3278,11 @@ def _handle_event(
             )
             self._emit_aliased_event(event, "authentication_updated", response)
             return
+
+        if "prefix-resources" in _diff.added or "prefix-resources" in _diff.changed:
+            logger.info(f"prefix resources updated for {response.resource} at {datetime.now()}")
+            getattr(self.on, "prefix_resources_changed").emit(
+                event.relation, app=event.app, unit=event.unit, response=response
+            )
+            self._emit_aliased_event(event, "prefix_resources_changed", response)
+            return
diff --git a/tests/v0/integration/database-charm/src/charm.py b/tests/v0/integration/database-charm/src/charm.py
index 9c1e23fb..50e5b2c4 100755
--- a/tests/v0/integration/database-charm/src/charm.py
+++ b/tests/v0/integration/database-charm/src/charm.py
@@ -194,7 +194,7 @@ def _on_database_pebble_ready(self, event: WorkloadEvent) -> None:
                     "command": "/usr/local/bin/docker-entrypoint.sh postgres",
                     "startup": "enabled",
                     "environment": {
-                        "PGDATA": "/var/lib/postgresql/data/pgdata",
+                        "PGDATA": "/var/lib/postgresql/data/pgdata/data",
                         "POSTGRES_PASSWORD": self._stored.password,
                     },
                 }
diff --git a/tests/v1/integration/application-charm/metadata.yaml b/tests/v1/integration/application-charm/metadata.yaml
index 46cd4de1..bfdd79c3 100644
--- a/tests/v1/integration/application-charm/metadata.yaml
+++ b/tests/v1/integration/application-charm/metadata.yaml
@@ -12,6 +12,8 @@ requires:
     interface: database_client
   first-database-roles:
     interface: database_client
+  first-database-username:
+    interface: database_client
   second-database-db:
     interface: database_client
   multiple-database-clusters:
@@ -36,4 +38,6 @@ requires:
   etcd-client:
     interface: etcd_client
   certificates:
-    interface: tls-certificates
\ No newline at end of file
+    interface: tls-certificates
+  database-with-prefix:
+    interface: database_client
diff --git a/tests/v1/integration/application-charm/src/charm.py b/tests/v1/integration/application-charm/src/charm.py
index 44b0d69d..5a87db36 100755
--- a/tests/v1/integration/application-charm/src/charm.py
+++ b/tests/v1/integration/application-charm/src/charm.py
@@ -120,6 +120,20 @@ def __init__(self, *args):
             self._on_first_database_auth_updated,
         )
 
+        self.first_database_username = ResourceRequirerEventHandler(
+            self,
+            "first-database-username",
+            requests=[
+                RequirerCommonModel(
+                    resource=database_name, entity_type="USER", entity_name="testuser"
+                )
+            ],
+            response_model=ExtendedResponseModel,
+        )
+        self.framework.observe(
+            self.first_database.on.resource_created, self._on_first_database_created
+        )
+
         # Events related to the second database that is requested
         # (these events are defined in the database requires charm library).
         database_name = f"{self.app.name.replace('-', '_')}_second_database_db"
@@ -163,6 +177,17 @@ def __init__(self, *args):
             self._on_cluster_endpoints_changed,
         )
 
+        self.database_prefixes = ResourceRequirerEventHandler(
+            charm=self,
+            relation_name="database-with-prefix",
+            requests=[
+                RequirerCommonModel(
+                    resource="testdb*", extra_user_roles=EXTRA_USER_ROLES, prefix_matching="all"
+                )
+            ],
+            response_model=ExtendedResponseModel,
+        )
+
         # Multiple database clusters charm events (defined dynamically
         # in the database requires charm library, using the provided cluster/relation aliases).
         database_name = f"{self.app.name.replace('-', '_')}_aliased_multiple_database_clusters"
diff --git a/tests/v1/integration/backward-compatibility-charm/metadata.yaml b/tests/v1/integration/backward-compatibility-charm/metadata.yaml
index 898da718..68a5d11d 100644
--- a/tests/v1/integration/backward-compatibility-charm/metadata.yaml
+++ b/tests/v1/integration/backward-compatibility-charm/metadata.yaml
@@ -10,3 +10,5 @@ summary: |
 requires:
   backward-database:
     interface: database_client
+  backward-prefix-database:
+    interface: database_client
diff --git a/tests/v1/integration/backward-compatibility-charm/src/charm.py b/tests/v1/integration/backward-compatibility-charm/src/charm.py
index e0f025c2..faa75fed 100755
--- a/tests/v1/integration/backward-compatibility-charm/src/charm.py
+++ b/tests/v1/integration/backward-compatibility-charm/src/charm.py
@@ -35,6 +35,16 @@ def __init__(self, *args):
         self.database = DatabaseRequires(self, "backward-database", "bwclient")
         self.framework.observe(self.database.on.database_created, self._on_resource_created)
 
+        self.database_prefixes = DatabaseRequires(
+            charm=self,
+            relation_name="backward-prefix-database",
+            database_name="testdb*",
+            requested_entity_name="testuser",
+        )
+        self.framework.observe(
+            self.database_prefixes.on.database_created, self._on_resource_created
+        )
+
     def _on_start(self, _) -> None:
         """Only sets an active status."""
         self.unit.status = ActiveStatus("Backward compatibility charm ready!")
diff --git a/tests/v1/integration/database-charm/src/charm.py b/tests/v1/integration/database-charm/src/charm.py
index e200083a..d86e6397 100755
--- a/tests/v1/integration/database-charm/src/charm.py
+++ b/tests/v1/integration/database-charm/src/charm.py
@@ -208,7 +208,7 @@ def _on_database_pebble_ready(self, event: WorkloadEvent) -> None:
                     "command": "/usr/local/bin/docker-entrypoint.sh postgres",
                     "startup": "enabled",
                     "environment": {
-                        "PGDATA": "/var/lib/postgresql/data/pgdata",
+                        "PGDATA": "/var/lib/postgresql/data/pgdata/data",
                         "POSTGRES_PASSWORD": self._stored.password,
                     },
                 }
@@ -228,9 +228,15 @@ def _on_resource_requested(self, event: ResourceRequestedEvent) -> None:
 
         resource = request.resource
         extra_user_roles = request.extra_user_roles
+        username = request.entity_name
+        password = request.entity_password
 
-        username = f"relation_{relation_id}_{request.request_id}"
-        password = self._new_password()
+        if resource[-1] == "*":
+            resources = [f"{resource[:-1]}1", f"{resource[:-1]}2"]
+        else:
+            resources = [resource]
+        username = username or f"relation_{relation_id}_{request.request_id}"
+        password = password or self._new_password()
         connection_string = (
             "dbname='postgres' user='postgres' host='localhost' "
             f"password='{self._stored.password}' connect_timeout=10"
@@ -238,13 +244,14 @@ def _on_resource_requested(self, event: ResourceRequestedEvent) -> None:
         connection = psycopg2.connect(connection_string)
         connection.autocommit = True
         cursor = connection.cursor()
-        # Create the database, user and password. Also gives the user access to the database.
-        cursor.execute(f"CREATE DATABASE {resource};")
         cursor.execute(f"CREATE USER {username} WITH ENCRYPTED PASSWORD '{password}';")
-        cursor.execute(f"GRANT ALL PRIVILEGES ON DATABASE {resource} TO {username};")
-        # Add the roles to the user.
-        if extra_user_roles:
-            cursor.execute(f"ALTER USER {username} {extra_user_roles};")
+        # Create the database, user and password. Also gives the user access to the database.
+        for resource in resources:
+            cursor.execute(f"CREATE DATABASE {resource};")
+            cursor.execute(f"GRANT ALL PRIVILEGES ON DATABASE {resource} TO {username};")
+            # Add the roles to the user.
+            if extra_user_roles:
+                cursor.execute(f"ALTER USER {username} {extra_user_roles};")
         # Get the database version.
         cursor.execute("SELECT version();")
         version = cursor.fetchone()[0]
@@ -272,6 +279,7 @@ def _on_resource_requested(self, event: ResourceRequestedEvent) -> None:
             username=username,
             endpoints=f"{self.model.get_binding('database').network.bind_address}:5432",
             version=version,
+            prefix_resources=",".join(resources) if len(resources) > 1 else None,
         )
         self.database.set_response(event.relation.id, response)
         self.unit.status = ActiveStatus()
@@ -294,8 +302,11 @@ def _on_resource_entity_requested(self, event: ResourceEntityRequestedEvent) ->
         entity_type = request.entity_type
 
         # Generate a entity-name and a entity-password for the application.
-        rolename = self._new_rolename()
-        password = self._new_password()
+        rolename = request.entity_name
+        password = request.entity_password
+
+        rolename = rolename or self._new_rolename()
+        password = password or self._new_password()
 
         # Connect to the database.
         connection_string = (
diff --git a/tests/v1/integration/test_backward_compatibility_charm.py b/tests/v1/integration/test_backward_compatibility_charm.py
index bde843f7..84a08247 100644
--- a/tests/v1/integration/test_backward_compatibility_charm.py
+++ b/tests/v1/integration/test_backward_compatibility_charm.py
@@ -89,3 +89,39 @@ async def test_backward_relation_with_charm_libraries_secrets(ops_test: OpsTest)
     assert len(password) == 16
     assert endpoints
     assert database == "bwclient"
+
+
+@pytest.mark.abort_on_fail
+async def test_backward_relation_with_prefix_and_username(ops_test: OpsTest):
+    prefix_relation = "backward-prefix-database"
+    # Relate the charms and wait for them exchanging some connection data.
+    await ops_test.model.add_relation(
+        DATABASE_APP_NAME, f"{APPLICATION_APP_NAME}:{prefix_relation}"
+    )
+    await ops_test.model.wait_for_idle(apps=APP_NAMES, status="active")
+
+    # check unit message to check if the topic_created_event is triggered
+    for unit in ops_test.model.applications[APPLICATION_APP_NAME].units:
+        assert unit.workload_status_message == "backward_database_created"
+
+    # Get the requests
+    secret_uri = (
+        await get_application_relation_data(
+            ops_test, APPLICATION_APP_NAME, prefix_relation, f"{PROV_SECRET_PREFIX}user"
+        )
+        or ""
+    )
+    secret_data = await get_juju_secret(ops_test, secret_uri)
+    username = secret_data["username"]
+    password = secret_data["password"]
+    endpoints = await get_application_relation_data(
+        ops_test, APPLICATION_APP_NAME, prefix_relation, "endpoints"
+    )
+    prefix_databases = await get_application_relation_data(
+        ops_test, APPLICATION_APP_NAME, prefix_relation, "prefix-databases"
+    )
+
+    assert username == "testuser"
+    assert len(password) == 16
+    assert endpoints
+    assert prefix_databases == "testdb1,testdb2"
diff --git a/tests/v1/integration/test_charm.py b/tests/v1/integration/test_charm.py
index 1529adc9..f56711d8 100644
--- a/tests/v1/integration/test_charm.py
+++ b/tests/v1/integration/test_charm.py
@@ -41,6 +41,8 @@
 DB_FIRST_DATABASE_RELATION_NAME = "first-database-db"
 DB_SECOND_DATABASE_RELATION_NAME = "second-database-db"
 ROLES_FIRST_DATABASE_RELATION_NAME = "first-database-roles"
+USERNAME_FIRST_DATABASE_RELATION_NAME = "first-database-username"
+PREFIX_DATABASE_RELATION_NAME = "database-with-prefix"
 
 MULTIPLE_DATABASE_CLUSTERS_RELATION_NAME = "multiple-database-clusters"
 ALIASED_MULTIPLE_DATABASE_CLUSTERS_RELATION_NAME = "aliased-multiple-database-clusters"
@@ -765,6 +767,33 @@ async def test_database_roles_relation_with_charm_libraries_secrets(ops_test: Op
     assert entity_pass is not None
 
 
+@pytest.mark.abort_on_fail
+@pytest.mark.usefixtures("only_with_juju_secrets")
+async def test_database_username(ops_test: OpsTest):
+    """Test basic functionality of database-roles relation interface."""
+    # Relate the charms and wait for them exchanging some connection data.
+
+    pytest.first_database_relation = await ops_test.model.add_relation(
+        f"{APPLICATION_APP_NAME}:{USERNAME_FIRST_DATABASE_RELATION_NAME}", DATABASE_APP_NAME
+    )
+    await ops_test.model.wait_for_idle(apps=APP_NAMES, status="active")
+
+    requests = json.loads(
+        await get_application_relation_data(
+            ops_test, APPLICATION_APP_NAME, USERNAME_FIRST_DATABASE_RELATION_NAME, "requests"
+        )
+        or "[]"
+    )
+    request = requests[0]
+    secret_uri = request.get(f"{SECRET_REF_PREFIX}entity")
+    secret_content = await get_juju_secret(ops_test, secret_uri)
+    entity_name = secret_content["entity-name"]
+    entity_pass = secret_content["entity-password"]
+
+    assert entity_name == "testuser"
+    assert entity_pass is not None
+
+
 async def test_an_application_can_connect_to_multiple_database_clusters(
     ops_test: OpsTest, database_charm
 ):
@@ -1370,3 +1399,30 @@ async def test_scaling_requires_can_access_shared_secrets(ops_test):
     await action.wait()
     new_password = action.results.get("value")
     assert new_password == orig_password
+
+
+@pytest.mark.abort_on_fail
+async def test_database_prefix(ops_test: OpsTest):
+    """Test basic functionality of database-roles relation interface."""
+    # Relate the charms and wait for them exchanging some connection data.
+
+    pytest.first_database_relation = await ops_test.model.add_relation(
+        f"{APPLICATION_APP_NAME}:{PREFIX_DATABASE_RELATION_NAME}", DATABASE_APP_NAME
+    )
+    await ops_test.model.wait_for_idle(apps=APP_NAMES, status="active")
+
+    requests = json.loads(
+        await get_application_relation_data(
+            ops_test, APPLICATION_APP_NAME, PREFIX_DATABASE_RELATION_NAME, "requests"
+        )
+        or "[]"
+    )
+    request = requests[0]
+
+    assert request["prefix-resources"] == "testdb1,testdb2"
+    data = json.loads(
+        await get_application_relation_data(
+            ops_test, APPLICATION_APP_NAME, PREFIX_DATABASE_RELATION_NAME, "data"
+        )
+    )
+    assert data[request["request-id"]]["prefix-matching"] == "all"
diff --git a/tests/v1/unit/test_data_interfaces.py b/tests/v1/unit/test_data_interfaces.py
index 30f49ef3..85899494 100644
--- a/tests/v1/unit/test_data_interfaces.py
+++ b/tests/v1/unit/test_data_interfaces.py
@@ -950,6 +950,10 @@ def __init__(self, *args):
             self.requirer.on.cluster1_resource_created,
             self._on_cluster1_resource_created,
         )
+        self.framework.observe(
+            self.requirer.on.prefix_resources_changed,
+            self._on_prefix_resources_changed,
+        )
 
     def log_relation_size(self, prefix=""):
         logger.info(f"§{prefix} relations: {len(self.requirer.interface.relations)}")
@@ -993,6 +997,9 @@ def _on_endpoints_changed(self, _) -> None:
     def _on_read_only_endpoints_changed(self, _) -> None:
         self.log_relation_size("on_read_only_endpoints_changed")
 
+    def _on_prefix_resources_changed(self, _) -> None:
+        self.log_relation_size("on_prefix_resources_changed")
+
     def _on_cluster1_resource_created(self, _) -> None:
         self.log_relation_size("on_cluster1_resource_created")
 
@@ -1010,6 +1017,7 @@ def reset_aliases():
             delattr(ResourceRequiresEvents, f"{cluster_alias}_resource_entity_created")
             delattr(ResourceRequiresEvents, f"{cluster_alias}_endpoints_changed")
             delattr(ResourceRequiresEvents, f"{cluster_alias}_read_only_endpoints_changed")
+            delattr(ResourceRequiresEvents, f"{cluster_alias}_prefix_resources_changed")
         except AttributeError:
             # Ignore the events not existing before the first test.
             pass
@@ -1090,6 +1098,13 @@ def test_relation_interface_consistency(self):
         with pytest.raises(ValidationError):
             KafkaRequestModel(consumer_group_prefix="*")
 
+    def test_requested_entity_consistency(self):
+        """Test consistency restrictions on direct secret usage and helper values."""
+        # Try to set password without entity name
+        with pytest.raises(ValueError) as e:
+            RequirerCommonModel(entity_password="testpass")
+        assert "Unable to set entity password without an entity name" in str(e.value)
+
 
 class TestDatabaseRequiresNoRelations(DataRequirerBaseTests, unittest.TestCase):
     metadata = METADATA
@@ -1197,10 +1212,12 @@ def test_requires_interface_functions_secrets(self):
                     "external-node-connectivity": False,
                     "extra-group-roles": None,
                     "extra-user-roles": "CREATEDB,CREATEROLE",
+                    "prefix-matching": None,
                     "request-id": "c759221a6c14c72a",
                     "resource": "data_platform",
                     "salt": "kkkkkkkk",
                     "secret-mtls": None,
+                    "secret-requested-entity": None,
                 },
                 {
                     "entity-permissions": None,
@@ -1208,10 +1225,12 @@ def test_requires_interface_functions_secrets(self):
                     "external-node-connectivity": False,
                     "extra-group-roles": None,
                     "extra-user-roles": None,
+                    "prefix-matching": None,
                     "request-id": "9ecfabfbb5258f88",
                     "resource": "",
                     "salt": "xxxxxxxx",
                     "secret-mtls": None,
+                    "secret-requested-entity": None,
                 },
             ],
         }
@@ -1459,16 +1478,19 @@ def test_fetch_my_relation_data_and_fields_secrets(self):
                     "entity-permissions": None,
                     "entity-type": None,
                     "salt": "kkkkkkkk",
+                    "prefix-matching": None,
                     "request-id": "c759221a6c14c72a",
                     "resource": "data_platform",
                     "extra-group-roles": None,
                     "extra-user-roles": "CREATEDB,CREATEROLE",
                     "external-node-connectivity": False,
                     "secret-mtls": None,
+                    "secret-requested-entity": None,
                 },
                 {
                     "entity-permissions": None,
                     "salt": "xxxxxxxx",
+                    "prefix-matching": None,
                     "request-id": "9ecfabfbb5258f88",
                     "resource": "",
                     "entity-type": "USER",
@@ -1476,6 +1498,7 @@ def test_fetch_my_relation_data_and_fields_secrets(self):
                     "extra-user-roles": None,
                     "external-node-connectivity": False,
                     "secret-mtls": None,
+                    "secret-requested-entity": None,
                 },
             ],
         }
@@ -1702,6 +1725,87 @@ def test_additional_fields_are_accessible(self, _on_resource_created):
         assert event.response.uris == "host1:port,host2:port"
         assert event.response.version == "1.0"
 
+    @patch.object(charm, "_on_prefix_resources_changed")
+    @pytest.mark.usefixtures("only_with_juju_secrets")
+    def test_on_prefix_resources_changed(self, _on_prefix_resources_changed):
+        """Asserts that the prefix resources are in the relation databag when they change."""
+        # Simulate adding endpoints to the relation.
+        self.harness.update_relation_data(
+            self.rel_id,
+            self.provider,
+            {
+                "requests": json.dumps(
+                    [
+                        {
+                            "salt": "kkkkkkkk",
+                            "request-id": "c759221a6c14c72a",
+                            "prefix-resources": "db1,db2",
+                        }
+                    ]
+                ),
+                "data": json.dumps(
+                    {
+                        "c759221a6c14c72a": {
+                            "salt": "kkkkkkkk",
+                            "request-id": "c759221a6c14c72a",
+                            "resource": DATABASE,
+                        }
+                    }
+                ),
+            },
+        )
+
+        # Assert the correct hook is called.
+        _on_prefix_resources_changed.assert_called_once()
+
+        # Check that the endpoints are present in the relation
+        # using the requires charm library event.
+        event = _on_prefix_resources_changed.call_args[0][0]
+        assert event.response.prefix_resources == "db1,db2"
+
+        # Reset the mock call count.
+        _on_prefix_resources_changed.reset_mock()
+
+        # Set the same data in the relation (no change in the endpoints).
+        self.harness.update_relation_data(
+            self.rel_id,
+            self.provider,
+            {
+                "requests": json.dumps(
+                    [
+                        {
+                            "salt": "kkkkkkkk",
+                            "request-id": "c759221a6c14c72a",
+                            "prefix-resources": "db1,db2",
+                        }
+                    ]
+                )
+            },
+        )
+
+        # Assert the hook was not called again.
+        _on_prefix_resources_changed.assert_not_called()
+
+        # Then, change the endpoints in the relation.
+        self.harness.update_relation_data(
+            self.rel_id,
+            self.provider,
+            {
+                "requests": json.dumps(
+                    [
+                        {
+                            "salt": "kkkkkkkk",
+                            "request-id": "c759221a6c14c72a",
+                            "prefix-resources": "db1,db2,db3",
+                        }
+                    ]
+                )
+            },
+        )
+
+        # Assert the hook is called now.
+        _on_prefix_resources_changed.assert_called_once()
+
     def test_assign_relation_alias(self):
         """Asserts the correct relation alias is assigned to the relation."""
         unit_name = f"{self.app_name}/0"