diff --git a/slo_generator/backends/cloud_monitoring_mql.py b/slo_generator/backends/cloud_monitoring_mql.py
index 56ea49ba..1e934f98 100644
--- a/slo_generator/backends/cloud_monitoring_mql.py
+++ b/slo_generator/backends/cloud_monitoring_mql.py
@@ -17,19 +17,19 @@
 """
 import logging
 import pprint
-import re
 import typing
 import warnings
 from collections import OrderedDict
-from typing import List, Tuple
+from datetime import datetime
+from typing import List, Optional, Tuple
 
 from google.api.distribution_pb2 import Distribution
+from google.cloud.monitoring_v3 import QueryTimeSeriesRequest
 from google.cloud.monitoring_v3.services.query_service import QueryServiceClient
 from google.cloud.monitoring_v3.services.query_service.pagers import (
     QueryTimeSeriesPager,
 )
-from google.cloud.monitoring_v3.types import metric_service
-from google.cloud.monitoring_v3.types.metric import TimeSeriesData
+from google.cloud.monitoring_v3.types.metric import TimeSeries
 
 from slo_generator.constants import NO_DATA
 
@@ -56,7 +56,7 @@ def __init__(self, project_id: str, client: QueryServiceClient = None):
 
     def good_bad_ratio(
         self,
-        timestamp: int,  # pylint: disable=unused-argument
+        timestamp: int,
         window: int,
         slo_config: dict,
     ) -> Tuple[int, int]:
@@ -73,22 +73,20 @@ def good_bad_ratio(
         """
         measurement: dict = slo_config["spec"]["service_level_indicator"]
         filter_good: str = measurement["filter_good"]
-        filter_bad: typing.Optional[str] = measurement.get("filter_bad")
-        filter_valid: typing.Optional[str] = measurement.get("filter_valid")
+        filter_bad: Optional[str] = measurement.get("filter_bad")
+        filter_valid: Optional[str] = measurement.get("filter_valid")
 
         # Query 'good events' timeseries
-        good_ts: List[TimeSeriesData] = self.query(query=filter_good, window=window)
+        good_ts: List[TimeSeries] = self.query(timestamp, window, filter_good)
         good_event_count: int = CM.count(good_ts)
 
         # Query 'bad events' timeseries
         bad_event_count: int
         if filter_bad:
-            bad_ts: List[TimeSeriesData] = self.query(query=filter_bad, window=window)
+            bad_ts: List[TimeSeries] = self.query(timestamp, window, filter_bad)
             bad_event_count = CM.count(bad_ts)
         elif filter_valid:
-            valid_ts: List[TimeSeriesData] = self.query(
-                query=filter_valid, window=window
-            )
+            valid_ts: List[TimeSeries] = self.query(timestamp, window, filter_valid)
             bad_event_count = CM.count(valid_ts) - good_event_count
         else:
             raise Exception("One of `filter_bad` or `filter_valid` is required.")
@@ -124,7 +122,7 @@ def distribution_cut(
         )
 
         # Query 'valid' events
-        series = self.query(query=filter_valid, window=window)
+        series = self.query(timestamp, window, filter_valid)
 
         if not series:
             return NO_DATA, NO_DATA  # no timeseries
@@ -193,38 +191,66 @@ def query_sli(
         """
         measurement: dict = slo_config["spec"]["service_level_indicator"]
         query: str = measurement["query"]
-        series: List[TimeSeriesData] = self.query(query=query, window=window)
+        series: List[TimeSeries] = self.query(timestamp, window, query)
         sli_value: float = series[0].point_data[0].values[0].double_value
         LOGGER.debug(f"SLI value: {sli_value}")
         return sli_value
 
-    def query(self, query: str, window: int) -> List[TimeSeriesData]:
+    def query(self, timestamp: float, window: int, query: str) -> List[TimeSeries]:
         """Query timeseries from Cloud Monitoring using MQL.
 
         Args:
-            query (str): MQL query.
+            timestamp (float): Current timestamp.
             window (int): Window size (in seconds).
-
+            query (str): MQL query.
         Returns:
             list: List of timeseries objects.
         """
-        # Enrich query to aggregate and reduce the time series over the
-        # desired window.
-        formatted_query: str = self._fmt_query(query, window)
-        request = metric_service.QueryTimeSeriesRequest(
-            {"name": self.parent, "query": formatted_query}
+        # Enrich query to aggregate and reduce time series over target window.
+        query_with_time_horizon_and_period: str = (
+            self.enrich_query_with_time_horizon_and_period(timestamp, window, query)
+        )
+        request = QueryTimeSeriesRequest(
+            {"name": self.parent, "query": query_with_time_horizon_and_period}
         )
         # fmt: off
         timeseries_pager: QueryTimeSeriesPager = (
             self.client.query_time_series(request)  # type: ignore[union-attr]
         )
         # fmt: on
-        timeseries: list = list(timeseries_pager)  # convert pager to flat list
+        timeseries: List[TimeSeries] = list(timeseries_pager)
         LOGGER.debug(pprint.pformat(timeseries))
         return timeseries
 
     @staticmethod
-    def count(timeseries: List[TimeSeriesData]) -> int:
+    def enrich_query_with_time_horizon_and_period(
+        timestamp: float,
+        window: int,
+        query: str,
+    ) -> str:
+        """Enrich MQL query with time period and horizon.
+        Args:
+            timestamp (float): UNIX timestamp.
+            window (int): Query window (in seconds).
+            query (str): Base query in YAML config.
+        Returns:
+            str: Enriched query.
+        """
+        # Python uses floating point numbers to represent time in seconds since the
+        # epoch, in UTC, with decimal part representing nanoseconds.
+        # MQL expects dates formatted like "%Y/%m/%d %H:%M:%S" or "%Y/%m/%d-%H:%M:%S".
+        # Reference: https://cloud.google.com/monitoring/mql/reference#lexical-elements
+        end_time_str: str = datetime.fromtimestamp(timestamp).strftime(
+            "%Y/%m/%d %H:%M:%S"
+        )
+        query_with_time_horizon_and_period: str = (
+            query
+            + f"| group_by [] | within {window}s, d'{end_time_str}' | every {window}s"
+        )
+        return query_with_time_horizon_and_period
+
+    @staticmethod
+    def count(timeseries: List[TimeSeries]) -> int:
         """Count events in time series assuming it was aligned with ALIGN_SUM
         and reduced with REDUCE_SUM (default).
 
@@ -240,43 +266,5 @@ def count(timeseries: List[TimeSeriesData]) -> int:
             LOGGER.debug(exception, exc_info=True)
             return NO_DATA  # no events in timeseries
 
-    @staticmethod
-    def _fmt_query(query: str, window: int) -> str:
-        """Format MQL query:
-
-        * If the MQL expression has a `window` placeholder, replace it by the
-        current window. Otherwise, append it to the expression.
-
-        * If the MQL expression has a `every` placeholder, replace it by the
-        current window. Otherwise, append it to the expression.
-
-        * If the MQL expression has a `group_by` placeholder, replace it.
-        Otherwise, append it to the expression.
-
-        Args:
-            query (str): Original query in YAMLconfig.
-            window (int): Query window (in seconds).
-
-        Returns:
-            str: Formatted query.
-        """
-        formatted_query: str = query.strip()
-        if "group_by" in formatted_query:
-            formatted_query = re.sub(
-                r"\|\s+group_by\s+\[.*\]\s*", "| group_by [] ", formatted_query
-            )
-        else:
-            formatted_query += "| group_by [] "
-        for mql_time_interval_keyword in ["within", "every"]:
-            if mql_time_interval_keyword in formatted_query:
-                formatted_query = re.sub(
-                    rf"\|\s+{mql_time_interval_keyword}\s+\w+\s*",
-                    f"| {mql_time_interval_keyword} {window}s ",
-                    formatted_query,
-                )
-            else:
-                formatted_query += f"| {mql_time_interval_keyword} {window}s "
-        return formatted_query.strip()
-
 
 CM = CloudMonitoringMqlBackend
diff --git a/tests/unit/backends/test_cloud_monitoring_mql.py b/tests/unit/backends/test_cloud_monitoring_mql.py
index 9e5e9d2e..addb6ef3 100644
--- a/tests/unit/backends/test_cloud_monitoring_mql.py
+++ b/tests/unit/backends/test_cloud_monitoring_mql.py
@@ -20,42 +20,28 @@
 
 
 class TestCloudMonitoringMqlBackend(unittest.TestCase):
-    def test_fmt_query(self):
-        queries = [
-            """  fetch gae_app
-      | metric 'appengine.googleapis.com/http/server/response_count'
-      | filter resource.project_id == '${GAE_PROJECT_ID}'
-      | filter
-          metric.response_code == 429
-          || metric.response_code == 200
-      | group_by [metric.response_code] | within 1h   """,
-            """ fetch gae_app
-      | metric 'appengine.googleapis.com/http/server/response_count'
-      | filter resource.project_id == '${GAE_PROJECT_ID}'
-      | filter
-          metric.response_code == 429
-          || metric.response_code == 200
-      | group_by [metric.response_code,  response_code_class]
-      | within 1h
-      | every 1h  """,
-            """ fetch gae_app
-      | metric 'appengine.googleapis.com/http/server/response_count'
-      | filter resource.project_id == '${GAE_PROJECT_ID}'
-      | filter
-          metric.response_code == 429
-          || metric.response_code == 200
-      | group_by [metric.response_code,response_code_class]
-      | within 1h
-      | every 1h """,
-        ]
+    def test_enrich_query_with_time_horizon_and_period(self):
+        timestamp: float = 1666995015.5144777  # = 2022/10/28 22:10:15.5144777
+        window: int = 3600  # in seconds
+        query: str = """fetch gae_app
+| metric 'appengine.googleapis.com/http/server/response_count'
+| filter resource.project_id == 'slo-generator-demo'
+| filter
+    metric.response_code == 429
+    || metric.response_code == 200
+"""
 
-        formatted_query = """fetch gae_app
-      | metric 'appengine.googleapis.com/http/server/response_count'
-      | filter resource.project_id == '${GAE_PROJECT_ID}'
-      | filter
-          metric.response_code == 429
-          || metric.response_code == 200
-      | group_by [] | within 3600s | every 3600s"""
+        enriched_query = """fetch gae_app
+| metric 'appengine.googleapis.com/http/server/response_count'
+| filter resource.project_id == 'slo-generator-demo'
+| filter
+    metric.response_code == 429
+    || metric.response_code == 200
+| group_by [] | within 3600s, d'2022/10/28 22:10:15' | every 3600s"""
 
-        for query in queries:
-            assert CloudMonitoringMqlBackend._fmt_query(query, 3600) == formatted_query
+        assert (
+            CloudMonitoringMqlBackend.enrich_query_with_time_horizon_and_period(
+                timestamp, window, query
+            )
+            == enriched_query
+        )