diff --git a/daemon.py b/daemon.py
index 842924e..68dca6b 100644
--- a/daemon.py
+++ b/daemon.py
@@ -17,6 +17,7 @@ from src.exchanges.boersenag import (
     HAMAExchange, HAMBExchange, HANAExchange, HANBExchange
 )
 from src.database.questdb_client import DatabaseClient
+from src.utils.validation import validate_exchange
 
 logging.basicConfig(
     level=logging.INFO,
@@ -67,6 +68,7 @@ STANDARD_EXCHANGES: List[Type[BaseExchange]] = [
 
 # Cache für existierende Trades pro Tag (wird nach jedem Exchange geleert)
 _existing_trades_cache = {}
+MAX_CACHE_SIZE = 50
 
 def get_trade_hash(trade):
     """Erstellt einen eindeutigen Hash für einen Trade."""
@@ -75,8 +77,9 @@ def get_trade_hash(trade):
 
 def get_existing_trades_for_day(db_url, exchange_name, day):
     """Holt existierende Trades für einen Tag aus der DB (mit Caching)."""
+    exchange_name = validate_exchange(exchange_name)
     cache_key = f"{exchange_name}_{day.strftime('%Y-%m-%d')}"
-    
+
     if cache_key in _existing_trades_cache:
         return _existing_trades_cache[cache_key]
     
@@ -109,6 +112,11 @@ def get_existing_trades_for_day(db_url, exchange_name, day):
     except Exception as e:
         logger.warning(f"Error fetching existing trades for {day}: {e}")
     
+    # Cache-Groesse begrenzen (FIFO via dict ordering, Python 3.7+)
+    if len(_existing_trades_cache) >= MAX_CACHE_SIZE:
+        oldest_key = next(iter(_existing_trades_cache))
+        del _existing_trades_cache[oldest_key]
+
     _existing_trades_cache[cache_key] = existing_trades
     return existing_trades
 
@@ -163,6 +171,7 @@ def filter_new_trades_batch(db_url, exchange_name, trades, batch_size=5000):
 
 def get_last_trade_timestamp(db_url: str, exchange_name: str) -> datetime.datetime:
     """Holt den Timestamp des letzten Trades für eine Exchange aus QuestDB."""
+    exchange_name = validate_exchange(exchange_name)
     query = f"trades where exchange = '{exchange_name}' latest by timestamp"
     try:
         response = requests.get(f"{db_url}/exec", params={'query': query}, auth=DB_AUTH)