diff --git a/backend/app/api/endpoints/recommendations.py b/backend/app/api/endpoints/recommendations.py
index 7c10f69..57c7f85 100644
--- a/backend/app/api/endpoints/recommendations.py
+++ b/backend/app/api/endpoints/recommendations.py
@@ -605,11 +605,22 @@ async def execute_auto_trading(db: AsyncSession = Depends(get_db)):
         total_processed = 0
         max_trades = 5
         
-        for rule_group in recommendations_response["recommendations_by_rule"]:
+        # make sure we iterate a list of rule group dicts
+        rec_groups = recommendations_response.get("recommendations_by_rule", [])
+        if isinstance(rec_groups, dict):
+            normalized = []
+            for name, grp in rec_groups.items():
+                if isinstance(grp, dict):
+                    normalized.append(grp)
+                else:
+                    normalized.append({"rule_name": name, "stocks": grp})
+            rec_groups = normalized
+
+        for rule_group in rec_groups:
             if total_processed >= max_trades:
                 break
                 
-            for stock in rule_group["stocks"][:settings.AUTO_TRADE_TOP_N_PER_RULE]:
+            for stock in rule_group.get("stocks", [])[:settings.AUTO_TRADE_TOP_N_PER_RULE]:
                 if total_processed >= max_trades:
                     break
                     
diff --git a/backend/app/models/models.py b/backend/app/models/models.py
index 904b19c..0d99835 100644
--- a/backend/app/models/models.py
+++ b/backend/app/models/models.py
@@ -128,7 +128,8 @@ class MarketData(Base):
     stock_code = Column(String(20), nullable=False, index=True)
     price = Column(Numeric(15, 2), nullable=False)
     change_rate = Column(Numeric(10, 4))
-    volume = Column(Integer)
+    # real‑time volume may also exceed int32; switch to bigint for safety
+    volume = Column(BigInteger)
     high_price = Column(Numeric(15, 2))
     low_price = Column(Numeric(15, 2))
     open_price = Column(Numeric(15, 2))
@@ -190,7 +191,8 @@ class StockAnalysis(Base):
     # 가격 정보
     current_price = Column(Integer, nullable=False)
     change_rate = Column(Numeric(10, 4))
-    volume = Column(Integer)
+    # volumes can exceed 32‑bit limits (e.g. 3 billion+), use bigint to avoid overflow
+    volume = Column(BigInteger)
     
     # 기술적 지표
     rsi = Column(Numeric(10, 4))
diff --git a/backend/app/services/trade_executor.py b/backend/app/services/trade_executor.py
index bde0b06..bf2a004 100644
--- a/backend/app/services/trade_executor.py
+++ b/backend/app/services/trade_executor.py
@@ -98,8 +98,20 @@ async def execute_auto_trade_background(recommendations_response: dict, db: Asyn
         result = await db.execute(select(Portfolio).where(Portfolio.quantity > 0))
         held_stocks = {p.stock_code for p in result.scalars().all()}
         
+        # normalize recommendations_by_rule early so we iterate over a list of groups
+        rec_groups = recommendations_response.get("recommendations_by_rule", [])
+        if isinstance(rec_groups, dict):
+            # older format: {rule_name: [stocks]}
+            normalized_list = []
+            for name, group in rec_groups.items():
+                if isinstance(group, dict):
+                    normalized_list.append(group)
+                else:
+                    normalized_list.append({"rule_name": name, "stocks": group})
+            rec_groups = normalized_list
+        
         unique_stocks = {}
-        for rule_group in recommendations_response.get("recommendations_by_rule", []):
+        for rule_group in rec_groups:
             # make sure we have a dict with expected keys
             if not isinstance(rule_group, dict):
                 logger.warning("Invalid rule_group in recommendations_response: %r", rule_group)
diff --git a/tests/test_volume_overflow.py b/tests/test_volume_overflow.py
new file mode 100644
index 0000000..dc6fd43
--- /dev/null
+++ b/tests/test_volume_overflow.py
@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""
+Verify that StockAnalysis and MarketData volume columns can handle values larger
+than 2**31-1. This script will fail prior to applying the bigint migration.
+"""
+import asyncio
+from datetime import date
+
+from app.core.database import AsyncSessionLocal
+from app.models.models import StockAnalysis, MarketData
+
+
+async def test_big_volume():
+    async with AsyncSessionLocal() as session:
+        # create and commit a record with a large volume value
+        huge_vol = 2962426126  # value that previously triggered overflow
+
+        sa = StockAnalysis(
+            stock_code="TEST",
+            stock_name="Test Corp",
+            analysis_date=date.today(),
+            current_price=100,
+            change_rate=0,
+            volume=huge_vol,
+        )
+        session.add(sa)
+
+        # also test MarketData
+        md = MarketData(
+            stock_code="TEST",
+            price=100,
+            change_rate=0,
+            volume=huge_vol,
+        )
+        session.add(md)
+
+        await session.commit()
+
+        print("Inserted records with large volume successfully")
+
+        # fetch back and verify
+        fetched_sa = await session.get(StockAnalysis, sa.id)
+        fetched_md = await session.get(MarketData, md.id)
+        print("StockAnalysis volume type:", type(fetched_sa.volume), fetched_sa.volume)
+        print("MarketData volume type:", type(fetched_md.volume), fetched_md.volume)
+
+        assert fetched_sa.volume == huge_vol
+        assert fetched_md.volume == huge_vol
+
+
+if __name__ == "__main__":
+    asyncio.run(test_big_volume())