diff --git a/src/memos/graph_dbs/polardb.py b/src/memos/graph_dbs/polardb.py
index a87c83510..d740ad1d2 100644
--- a/src/memos/graph_dbs/polardb.py
+++ b/src/memos/graph_dbs/polardb.py
@@ -247,15 +247,12 @@ def _warm_up_connections_by_all(self):
 
     @contextmanager
     def _get_connection(self):
+        import psycopg2
+
         timeout = self._connection_wait_timeout
-        if timeout <= 0:
-            self._semaphore.acquire()
-        else:
-            if not self._semaphore.acquire(timeout=timeout):
-                logger.warning(f"Timeout waiting for connection slot ({timeout}s)")
-                raise RuntimeError(
-                    f"Connection pool busy: acquire a slot within {timeout}s (all connections in use)."
-                )
+        if not self._semaphore.acquire(timeout=max(timeout, 0)):
+            logger.warning(f"Timeout waiting for connection slot ({timeout}s)")
+            raise RuntimeError("Connection pool busy")
         logger.info(
             "Connection pool usage: %s/%s",
             self.connection_pool.maxconn - self._semaphore._value,
@@ -263,17 +260,26 @@ def _get_connection(self):
         )
         conn = None
         broken = False
-
         try:
             conn = self.connection_pool.getconn()
-            logger.debug(f"Acquired connection {id(conn)} from pool")
             conn.autocommit = True
+            for attempt in range(2):
+                try:
+                    with conn.cursor() as cur:
+                        cur.execute("SELECT 1")
+                    break
+                except psycopg2.Error:
+                    logger.warning("Dead connection detected, recreating (attempt %d)", attempt + 1)
+                    self.connection_pool.putconn(conn, close=True)
+                    conn = self.connection_pool.getconn()
+                    conn.autocommit = True
+            else:
+                raise RuntimeError("Cannot obtain valid DB connection after 2 attempts")
             with conn.cursor() as cur:
                 cur.execute(f'SET search_path = {self.db_name}_graph, ag_catalog, "$user", public;')
             yield conn
-        except Exception as e:
+        except Exception:
             broken = True
-            logger.exception(f"Connection failed or broken: {e}")
             raise
         finally:
             if conn:
@@ -1814,7 +1820,7 @@ def search_by_fulltext(
                         properties = row[2]  # properties column
                         item.update(self._extract_fields_from_properties(properties, return_fields))
                     output.append(item)
-            elapsed = (time.perf_counter() - start_time) * 1000
+            elapsed = (time.perf_counter() - start_time) * 1000.0
             logger.info("search_by_fulltext internal took %.1f ms", elapsed)
             return output[:top_k]
 
@@ -1945,7 +1951,7 @@ def search_by_embedding(
                         properties = row[1]  # properties column
                         item.update(self._extract_fields_from_properties(properties, return_fields))
                     output.append(item)
-            elapsed_time = time.perf_counter() - start_time
+            elapsed_time = (time.perf_counter() - start_time) * 1000.0
             logger.info(
                 "search_by_embedding query embedding completed time took %.1f ms", elapsed_time
             )
@@ -2500,7 +2506,7 @@ def _extract_special_filter_values(filter_obj):
         except Exception as e:
             logger.error(f"[EXPORT GRAPH - NODES] Exception: {e}", exc_info=True)
             raise RuntimeError(f"[EXPORT GRAPH - NODES] Exception: {e}") from e
-        elapsed = (time.perf_counter() - start_time) * 1000
+        elapsed = (time.perf_counter() - start_time) * 1000.0
         logger.info("export internal took %.1f ms", elapsed)
 
         edges = []
@@ -3360,7 +3366,7 @@ def add_nodes_batch(
                             logger.warning(
                                 f"[add_nodes_batch] Failed to deallocate {prepare_name}: {dealloc_error}"
                             )
-                    elapsed_time = time.perf_counter() - batch_start_time
+                    elapsed_time = (time.perf_counter() - batch_start_time) * 1000.0
                     logger.info(
                         "add_nodes_batch batch insert completed successfully in took %.1f ms",
                         elapsed_time,
@@ -4815,7 +4821,7 @@ def delete_node_by_prams(
         """
         batch_start_time = time.time()
         logger.info(
-            f"[delete_node_by_prams] memory_ids: {memory_ids}, file_ids: {file_ids}, filter: {filter}, writable_cube_ids: {writable_cube_ids}"
+            f" delete_node_by_prams memory_ids: {memory_ids}, file_ids: {file_ids}, filter: {filter}, writable_cube_ids: {writable_cube_ids}"
         )
 
         # Build user_name condition from writable_cube_ids (OR relationship - match any cube_id)
@@ -4889,7 +4895,7 @@ def delete_node_by_prams(
                     DELETE FROM "{self.db_name}_graph"."Memory"
                     WHERE {where_clause}
                 """
-                logger.info(f"[delete_node_by_prams] delete_query: {delete_query}")
+                logger.info(f" delete_node_by_prams delete_query: {delete_query}")
 
                 cursor.execute(delete_query)
                 deleted_count = cursor.rowcount
@@ -4897,9 +4903,9 @@ def delete_node_by_prams(
 
                 logger.info(f"[delete_node_by_prams] Deleted {deleted_count} nodes")
 
-                elapsed_time = time.time() - batch_start_time
+                elapsed_time = (time.time() - batch_start_time) * 1000.0
                 logger.info(
-                    f"[delete_node_by_prams] Deletion completed successfully in {elapsed_time:.2f}s, total deleted {total_deleted_count} nodes"
+                    f"delete_node_by_prams Deletion completed successfully in {elapsed_time:.2f}s, total deleted {total_deleted_count} nodes"
                 )
         except Exception as e:
             logger.error(f"[delete_node_by_prams] Failed to delete nodes: {e}", exc_info=True)