diff --git a/src/upgrade.py b/src/upgrade.py
index 795aacf060..ad025364ff 100644
--- a/src/upgrade.py
+++ b/src/upgrade.py
@@ -6,6 +6,7 @@
 import json
 import logging
 
+from charmlibs import snap
 from charms.data_platform_libs.v0.upgrade import (
     ClusterNotReadyError,
     DataUpgrade,
@@ -18,15 +19,17 @@
 from tenacity import RetryError, Retrying, stop_after_attempt, wait_fixed
 from typing_extensions import override
 
+from cluster import SwitchoverFailedError
 from constants import (
     APP_SCOPE,
     MONITORING_PASSWORD_KEY,
     MONITORING_USER,
     PATRONI_PASSWORD_KEY,
+    POSTGRESQL_SNAP_NAME,
     RAFT_PASSWORD_KEY,
     SNAP_PACKAGES,
 )
-from utils import new_password
+from utils import new_password, snap_refreshed
 
 logger = logging.getLogger(__name__)
 
@@ -141,8 +144,52 @@ def _on_upgrade_charm_check_legacy(self) -> None:
                 self._prepare_upgrade_from_legacy()
             self.on.upgrade_charm.emit()
 
+    def _pre_upgrade_switchover(self, event: UpgradeGrantedEvent) -> bool:
+        """Switchover primary before upgrading, to minimize client write downtime.
+
+        Returns True if the event was deferred after the switchover (caller should return).
+        """
+        if len(self.peer_relation.units) == 0:
+            return False
+
+        if self.charm.async_replication.get_primary_cluster_endpoint():
+            logger.info("Standby cluster is read-only; skipping pre-upgrade switchover")
+            return False
+
+        if snap_refreshed(snap.SnapCache()[POSTGRESQL_SNAP_NAME].revision):
+            logger.info("Snap is already at the target revision, skipping pre-upgrade switchover")
+            return False
+
+        if self.unit_upgrade_data.get("pre-upgrade-switchover-done"):
+            self.unit_upgrade_data.update({"pre-upgrade-switchover-done": ""})
+            return False
+
+        old_primary = self.charm._patroni.get_primary()
+        if old_primary is None or old_primary != self.charm.unit.name.replace("/", "-"):
+            return False
+
+        logger.info("Switching over primary before upgrading")
+        self.charm.unit.status = MaintenanceStatus("switching over primary")
+        self.charm._patroni.switchover()
+        self.charm._patroni.primary_changed(old_primary)
+        logger.info("Primary switchover completed")
+
+        if self.charm.unit.is_leader():
+            self.charm._update_relation_endpoints()
+
+        self.unit_upgrade_data.update({"pre-upgrade-switchover-done": "true"})
+        logger.info("Deferring upgrade to let Juju commit endpoint changes to client relations")
+        event.defer()
+        return True
+
     @override
     def _on_upgrade_granted(self, event: UpgradeGrantedEvent) -> None:
+        try:
+            if self._pre_upgrade_switchover(event):
+                return
+        except (RetryError, SwitchoverFailedError) as e:
+            logger.warning("Pre-upgrade switchover failed: %s. Proceeding with upgrade.", e)
+
         # Refresh the charmed PostgreSQL snap and restart the database.
         # Update the configuration.
         self.charm.unit.status = MaintenanceStatus("updating configuration")
diff --git a/tests/unit/test_upgrade.py b/tests/unit/test_upgrade.py
index d9672a0a3a..914bd76de7 100644
--- a/tests/unit/test_upgrade.py
+++ b/tests/unit/test_upgrade.py
@@ -196,6 +196,23 @@ def test_on_upgrade_granted(harness):
         _updated_synchronous_node_count.assert_called_once_with()
 
 
+def test_pre_upgrade_switchover_skips_standby(harness):
+    with (
+        patch(
+            "charm.PostgreSQLAsyncReplication.get_primary_cluster_endpoint"
+        ) as _get_primary_cluster_endpoint,
+        patch("charm.Patroni.switchover") as _switchover,
+    ):
+        # A standby (async-replica) cluster is read-only: there is no client write
+        # downtime to avoid, so the pre-upgrade switchover must be skipped.
+        _get_primary_cluster_endpoint.return_value = "10.1.1.1"
+        mock_event = MagicMock()
+
+        assert harness.charm.upgrade._pre_upgrade_switchover(mock_event) is False
+        _switchover.assert_not_called()
+        mock_event.defer.assert_not_called()
+
+
 def test_pre_upgrade_check(harness):
     with (
         patch(