diff --git a/apps/api/src/services/signoz_client.py b/apps/api/src/services/signoz_client.py
index bf1107c3d..386bbde70 100644
--- a/apps/api/src/services/signoz_client.py
+++ b/apps/api/src/services/signoz_client.py
@@ -254,9 +254,7 @@ class SignOzClient:
         # =====================================================================
         # 使用 signoz_traces.distributed_signoz_index_v3 表
         # statusCode: 0=Unset, 1=Ok, 2=Error
-        # 計算 Unix 納秒時間戳 (ClickHouse DateTime64(9) 格式)
-        start_ns = int(start_time.timestamp() * 1_000_000_000)
-        end_ns = int(end_time.timestamp() * 1_000_000_000)
+        # 使用 INTERVAL 語法避免 Decimal overflow
 
         rps_query = f"""
         SELECT
@@ -264,7 +262,7 @@ class SignOzClient:
             countIf(statusCode = 2) as error_count
         FROM signoz_traces.distributed_signoz_index_v3
         WHERE
-            timestamp BETWEEN toDateTime64({start_ns}, 9) AND toDateTime64({end_ns}, 9)
+            timestamp > now() - INTERVAL {time_window_minutes} MINUTE
             AND serviceName LIKE '%{service_name}%'
         """
 
@@ -290,7 +288,7 @@ class SignOzClient:
             quantile(0.99)(durationNano / 1000000.0) as p99
         FROM signoz_traces.distributed_signoz_index_v3
         WHERE
-            timestamp BETWEEN toDateTime64({start_ns}, 9) AND toDateTime64({end_ns}, 9)
+            timestamp > now() - INTERVAL {time_window_minutes} MINUTE
             AND serviceName LIKE '%{service_name}%'
         """
 
@@ -305,14 +303,11 @@ class SignOzClient:
         # =====================================================================
         # Query 3: Trend Analysis (對比前一時間窗)
         # =====================================================================
-        prev_start_ns = int((start_time - timedelta(minutes=time_window_minutes)).timestamp() * 1_000_000_000)
-        prev_end_ns = start_ns
-
         trend_query = f"""
         SELECT count() as prev_requests
         FROM signoz_traces.distributed_signoz_index_v3
         WHERE
-            timestamp BETWEEN toDateTime64({prev_start_ns}, 9) AND toDateTime64({prev_end_ns}, 9)
+            timestamp BETWEEN now() - INTERVAL {time_window_minutes * 2} MINUTE AND now() - INTERVAL {time_window_minutes} MINUTE
             AND serviceName LIKE '%{service_name}%'
         """