diff --git a/database/init.sql b/database/init.sql
index 1019a74..ca67ad3 100644
--- a/database/init.sql
+++ b/database/init.sql
@@ -19,4 +19,62 @@ CREATE TABLE cml_metadata (
     PRIMARY KEY (cml_id, sublink_id)
 );
 
+CREATE TABLE cml_stats (
+    cml_id TEXT PRIMARY KEY,
+    total_records BIGINT,
+    valid_records BIGINT,
+    null_records BIGINT,
+    completeness_percent REAL,
+    min_rsl REAL,
+    max_rsl REAL,
+    mean_rsl REAL,
+    stddev_rsl REAL,
+    last_rsl REAL,
+    last_update TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE OR REPLACE FUNCTION update_cml_stats(target_cml_id TEXT) RETURNS VOID AS $$
+BEGIN
+    INSERT INTO cml_stats (
+        cml_id,
+        total_records,
+        valid_records,
+        null_records,
+        completeness_percent,
+        min_rsl,
+        max_rsl,
+        mean_rsl,
+        stddev_rsl,
+        last_rsl,
+        last_update
+    )
+    SELECT
+        cd.cml_id::text,
+        COUNT(*) as total_records,
+        COUNT(CASE WHEN cd.rsl IS NOT NULL THEN 1 END) as valid_records,
+        COUNT(CASE WHEN cd.rsl IS NULL THEN 1 END) as null_records,
+        ROUND(100.0 * COUNT(CASE WHEN cd.rsl IS NOT NULL THEN 1 END) / COUNT(*), 2) as completeness_percent,
+        MIN(cd.rsl) as min_rsl,
+        MAX(cd.rsl) as max_rsl,
+        ROUND(AVG(cd.rsl)::numeric, 2) as mean_rsl,
+        ROUND(STDDEV(cd.rsl)::numeric, 2) as stddev_rsl,
+        (SELECT rsl FROM cml_data WHERE cml_id = cd.cml_id ORDER BY time DESC LIMIT 1) as last_rsl,
+        NOW()
+    FROM cml_data cd
+    WHERE cd.cml_id = target_cml_id
+    GROUP BY cd.cml_id
+    ON CONFLICT (cml_id) DO UPDATE SET
+        total_records = EXCLUDED.total_records,
+        valid_records = EXCLUDED.valid_records,
+        null_records = EXCLUDED.null_records,
+        completeness_percent = EXCLUDED.completeness_percent,
+        min_rsl = EXCLUDED.min_rsl,
+        max_rsl = EXCLUDED.max_rsl,
+        mean_rsl = EXCLUDED.mean_rsl,
+        stddev_rsl = EXCLUDED.stddev_rsl,
+        last_rsl = EXCLUDED.last_rsl,
+        last_update = EXCLUDED.last_update;
+END;
+$$ LANGUAGE plpgsql;
+
 SELECT create_hypertable('cml_data', 'time');
\ No newline at end of file
diff --git a/grafana/provisioning/dashboards/definitions/cml-realtime.json b/grafana/provisioning/dashboards/definitions/cml-realtime.json
index fb3a8f4..6059cf5 100644
--- a/grafana/provisioning/dashboards/definitions/cml-realtime.json
+++ b/grafana/provisioning/dashboards/definitions/cml-realtime.json
@@ -392,7 +392,7 @@
                 "query": "SELECT DISTINCT cml_id::text FROM cml_metadata ORDER BY cml_id",
                 "refresh": 1,
                 "regex": "",
-                "skipUrlSync": true,
+                "skipUrlSync": false,
                 "sort": 0,
                 "tagValuesQuery": "",
                 "tagsQuery": "",
diff --git a/parser/db_writer.py b/parser/db_writer.py
index 1c00735..c410ba3 100644
--- a/parser/db_writer.py
+++ b/parser/db_writer.py
@@ -179,16 +179,41 @@ def _execute_batch_insert(
             psycopg2.extras.execute_values(
                 cur, sql, records, template=None, page_size=1000
             )
-            self.conn.commit()
+            # Do not commit here; caller will commit once to allow batching
             return len(records)
         except Exception:
-            self.conn.rollback()
+            try:
+                self.conn.rollback()
+            except Exception:
+                logger.exception("Failed rollback after %s error", operation_name)
             logger.exception("Failed to %s", operation_name)
             raise
         finally:
             if cur and not cur.closed:
                 cur.close()
 
+    def _update_stats_for_cmls(self, cml_ids: List[str]) -> None:
+        """Update cml_stats for the given CML IDs."""
+        if not cml_ids:
+            return
+
+        cur = self.conn.cursor()
+        try:
+            for cml_id in cml_ids:
+                cur.execute("SELECT update_cml_stats(%s)", (cml_id,))
+            # Do not commit here; caller should commit once after batch operations
+            logger.info("Executed update_cml_stats for %d CMLs", len(cml_ids))
+        except Exception:
+            try:
+                self.conn.rollback()
+            except Exception:
+                logger.exception("Rollback failed while handling stats update error")
+            logger.exception("Failed to update stats for CMLs: %s", cml_ids)
+            raise
+        finally:
+            if cur and not cur.closed:
+                cur.close()
+
     def write_metadata(self, df) -> int:
         """Write metadata DataFrame to `cml_metadata`.
 
@@ -229,12 +254,22 @@ def write_metadata(self, df) -> int:
             "length = EXCLUDED.length"
         )
 
-        return self._with_connection_retry(
+        rows_written = self._with_connection_retry(
             lambda: self._execute_batch_insert(
                 sql, records, "write metadata to database"
             )
         )
 
+        # Commit once after batch operation
+        try:
+            if self.conn:
+                self.conn.commit()
+        except Exception:
+            logger.exception("Failed to commit metadata write")
+            raise
+
+        return rows_written
+
     def write_rawdata(self, df) -> int:
         """Write raw time series DataFrame to `cml_data`.
 
@@ -253,10 +288,26 @@ def write_rawdata(self, df) -> int:
         )
         records = [tuple(x) for x in df_subset.to_numpy()]
 
+        # Get unique CML IDs for stats update
+        unique_cml_ids = df_subset["cml_id"].unique().tolist()
+
         sql = "INSERT INTO cml_data (time, cml_id, sublink_id, rsl, tsl) VALUES %s"
 
-        return self._with_connection_retry(
+        rows_written = self._with_connection_retry(
             lambda: self._execute_batch_insert(
                 sql, records, "write raw data to database"
             )
         )
+
+        # Update stats for affected CMLs and commit once afterward
+        if rows_written > 0 and unique_cml_ids:
+            self._update_stats_for_cmls(unique_cml_ids)
+
+        try:
+            if self.conn:
+                self.conn.commit()
+        except Exception:
+            logger.exception("Failed to commit raw data + stats update")
+            raise
+
+        return rows_written
diff --git a/parser/tests/test_db_writer.py b/parser/tests/test_db_writer.py
index a0e3788..73ffdf3 100644
--- a/parser/tests/test_db_writer.py
+++ b/parser/tests/test_db_writer.py
@@ -234,3 +234,86 @@ def test_close_already_closed():
 
     writer.close()  # Should not raise
     assert writer.conn is None
+
+
+def test_write_rawdata_execute_values_failure_triggers_rollback(mock_connection):
+    """When execute_values raises, write_rawdata should rollback and propagate."""
+    writer = DBWriter("postgresql://test")
+    writer.conn = mock_connection
+
+    df = pd.DataFrame(
+        {
+            "time": pd.to_datetime(["2026-01-22 10:00:00"]),
+            "cml_id": ["123"],
+            "sublink_id": ["A"],
+            "rsl": [-45.0],
+            "tsl": [1.0],
+        }
+    )
+
+    with patch(
+        "parser.db_writer.psycopg2.extras.execute_values",
+        side_effect=Exception("DB error"),
+    ):
+        with pytest.raises(Exception, match="DB error"):
+            writer.write_rawdata(df)
+
+    # rollback should have been called by the error handler
+    mock_connection.rollback.assert_called()
+
+
+def test_write_metadata_execute_values_failure_triggers_rollback(mock_connection):
+    """When execute_values raises during metadata write, rollback is performed."""
+    writer = DBWriter("postgresql://test")
+    writer.conn = mock_connection
+
+    df = pd.DataFrame(
+        {
+            "cml_id": ["123"],
+            "sublink_id": ["A"],
+            "site_0_lon": [13.4],
+            "site_0_lat": [52.5],
+            "site_1_lon": [13.6],
+            "site_1_lat": [52.7],
+            "frequency": [38.0],
+            "polarization": ["H"],
+            "length": [1200.0],
+        }
+    )
+
+    with patch(
+        "parser.db_writer.psycopg2.extras.execute_values",
+        side_effect=Exception("meta error"),
+    ):
+        with pytest.raises(Exception, match="meta error"):
+            writer.write_metadata(df)
+
+    mock_connection.rollback.assert_called()
+
+
+def test__update_stats_for_cmls_executes_queries_without_commit(mock_connection):
+    """Ensure _update_stats_for_cmls executes update function per CML and does not commit."""
+    writer = DBWriter("postgresql://test")
+    writer.conn = mock_connection
+
+    cml_ids = ["100", "200"]
+    writer._update_stats_for_cmls(cml_ids)
+
+    cur = mock_connection.cursor.return_value
+    assert cur.execute.call_count == len(cml_ids)
+    # commit should not be called by the helper
+    mock_connection.commit.assert_not_called()
+
+
+def test__update_stats_for_cmls_rollback_on_error(mock_connection):
+    """If executing update function raises, ensure rollback is attempted and exception propagated."""
+    writer = DBWriter("postgresql://test")
+    writer.conn = mock_connection
+
+    cur = mock_connection.cursor.return_value
+    cur.execute.side_effect = Exception("update failed")
+
+    with pytest.raises(Exception, match="update failed"):
+        writer._update_stats_for_cmls(["100"])
+
+    mock_connection.rollback.assert_called()
diff --git a/webserver/main.py b/webserver/main.py
index 661a2ae..f549aa8 100644
--- a/webserver/main.py
+++ b/webserver/main.py
@@ -18,9 +18,15 @@
 DATA_STAGED_FOR_PARSING_DIR = "/app/data_staged_for_parsing"
 DATA_ARCHIVED_DIR = "/app/data_archived"
 
-# Create directories if they don't exist
-for directory in [DATA_INCOMING_DIR, DATA_STAGED_FOR_PARSING_DIR, DATA_ARCHIVED_DIR]:
-    Path(directory).mkdir(parents=True, exist_ok=True)
+
+def ensure_data_directories():
+    """Create data directories if they don't exist."""
+    for directory in [
+        DATA_INCOMING_DIR,
+        DATA_STAGED_FOR_PARSING_DIR,
+        DATA_ARCHIVED_DIR,
+    ]:
+        Path(directory).mkdir(parents=True, exist_ok=True)
 
 
 def safe_float(value):
@@ -469,27 +475,28 @@ def api_cml_stats():
         cur = conn.cursor()
         cur.execute(
             """
-            WITH latest_60min AS (
-                SELECT cml_id, rsl, time
+            SELECT
+                cs.cml_id::text,
+                cs.total_records,
+                cs.valid_records,
+                cs.null_records,
+                cs.completeness_percent,
+                cs.min_rsl,
+                cs.max_rsl,
+                cs.mean_rsl,
+                cs.stddev_rsl,
+                cs.last_rsl,
+                ROUND(STDDEV(cd.rsl)::numeric, 2) as stddev_last_60min
+            FROM cml_stats cs
+            LEFT JOIN (
+                SELECT cml_id, rsl
                 FROM cml_data
                 WHERE time >= (SELECT MAX(time) FROM cml_data) - INTERVAL '60 minutes'
-            )
-            SELECT
-                cd.cml_id::text,
-                COUNT(*) as total_records,
-                COUNT(CASE WHEN cd.rsl IS NOT NULL THEN 1 END) as valid_records,
-                COUNT(CASE WHEN cd.rsl IS NULL THEN 1 END) as null_records,
-                ROUND(100.0 * COUNT(CASE WHEN cd.rsl IS NOT NULL THEN 1 END) / COUNT(*), 2) as completeness_percent,
-                MIN(cd.rsl) as min_rsl,
-                MAX(cd.rsl) as max_rsl,
-                ROUND(AVG(cd.rsl)::numeric, 2) as mean_rsl,
-                ROUND(STDDEV(cd.rsl)::numeric, 2) as stddev_rsl,
-                (SELECT rsl FROM cml_data WHERE cml_id = cd.cml_id ORDER BY time DESC LIMIT 1) as last_rsl,
-                ROUND(STDDEV(l60.rsl)::numeric, 2) as stddev_last_60min
-            FROM cml_data cd
-            LEFT JOIN latest_60min l60 ON cd.cml_id = l60.cml_id
-            GROUP BY cd.cml_id
-            ORDER BY cd.cml_id
+            ) cd ON cs.cml_id = cd.cml_id
+            GROUP BY cs.cml_id, cs.total_records, cs.valid_records, cs.null_records,
+                     cs.completeness_percent, cs.min_rsl, cs.max_rsl, cs.mean_rsl,
+                     cs.stddev_rsl, cs.last_rsl
+            ORDER BY cs.cml_id
         """
         )
         data = cur.fetchall()
@@ -800,6 +807,8 @@ def server_error(error):
 # ==================== START SERVER ====================
 
 if __name__ == "__main__":
+    # Create data directories
+    ensure_data_directories()
     # Wait for database to be ready
     time.sleep(10)
     app.run(host="0.0.0.0", port=5000, debug=True)
diff --git a/webserver/tests/test_api_cml_stats.py b/webserver/tests/test_api_cml_stats.py
new file mode 100644
index 0000000..5838380
--- /dev/null
+++ b/webserver/tests/test_api_cml_stats.py
@@ -0,0 +1,60 @@
+import sys
+from unittest.mock import Mock
+
+import pytest
+
+
+# Ensure optional heavy imports won't fail at import time
+sys.modules.setdefault("folium", Mock())
+sys.modules.setdefault("altair", Mock())
+sys.modules.setdefault("requests", Mock())
+
+
+def test_api_cml_stats_returns_cached_stats(monkeypatch):
+    # Make the webserver package modules importable (tests add webserver/ to sys.path)
+    import os
+
+    sys.path.insert(0, os.path.dirname(os.path.dirname(__file__)))
+
+    # Import main module from webserver package directory
+    import main as wm
+
+    # Prepare mock DB connection and cursor
+    mock_conn = Mock()
+    mock_cursor = Mock()
+    mock_conn.cursor.return_value = mock_cursor
+
+    # Row fields: cml_id, total_records, valid_records, null_records, completeness_percent,
+    # min_rsl, max_rsl, mean_rsl, stddev_rsl, last_rsl, stddev_last_60min
+    mock_cursor.fetchall.return_value = [
+        (
+            "10001",
+            10,
+            9,
+            1,
+            90.0,
+            -60.0,
+            -40.0,
+            -50.0,
+            3.0,
+            -45.0,
+            1.5,
+        )
+    ]
+
+    # Ensure cursor.close and conn.close exist
+    mock_cursor.close = Mock()
+    mock_conn.close = Mock()
+
+    monkeypatch.setattr(wm, "get_db_connection", lambda: mock_conn)
+
+    client = wm.app.test_client()
+    resp = client.get("/api/cml-stats")
+    assert resp.status_code == 200
+    data = resp.get_json()
+    assert isinstance(data, list)
+    assert len(data) == 1
+    row = data[0]
+    assert row["cml_id"] == "10001"
+    assert row["completeness_percent"] == 90.0
+    assert row["last_rsl"] == -45.0