web: make rate limiter storage uri configurable

web/core/config.py

@@ -67,6 +67,21 @@ def remotes_json_path(self) -> str:
         """Path to remotes.json configuration."""
         return os.path.join(self.base_dir, 'configs', 'remotes.json')
 
+    @property
+    def rate_limiter_storage_uri(self) -> str:
+        """
+        Storage URI for the rate limiter.
+
+        Uses CBS_RATE_LIMITER_STORAGE_URI env var if set and non-empty,
+        otherwise falls back to redis backend. When using the redis backend,
+        db index 1 is used to avoid conflicts with any other components that
+        use db index 0.
+        """
+        uri = os.getenv('CBS_RATE_LIMITER_STORAGE_URI', '').strip()
+        if uri:
+            return uri
+        return f"redis://{self.redis_host}:{self.redis_port}/1"
+
     @property
     def enable_inbuilt_builder(self) -> bool:
         """Whether to enable the inbuilt builder."""

web/core/limiter.py

@@ -10,13 +10,9 @@
 
 settings = get_settings()
 
-# We use the same redis instance which is used to store build metadata
-# and other cached data. To keep that data separate, we use db-1 of the
-# redis instance instead of the default db-0.
-REDIS_DB_NUMBER = 1
 limiter = Limiter(
     key_func=get_remote_address,
-    storage_uri=f"redis://{settings.redis_host}:{settings.redis_port}/{REDIS_DB_NUMBER}",
+    storage_uri=settings.rate_limiter_storage_uri,
     strategy="fixed-window",
 )