Defer decision ID fetch to after metadata message

Decision IDs are now loaded inside the streaming generators after
the metadata message is yielded, eliminating a blocking DB query
from the pre-stream path (~100-200ms improvement to TTFB).

api/app.py

@@ -273,8 +273,7 @@ async def _stream_from_cache(
     query_parameters: QueryParameters,
     batch_size: int,
     limit: int | None,
-    disliked_ids: set[int] | None = None,
+    user_email: str | None = None,
-    liked_ids: set[int] | None = None,
     decision_filter: str = "all",
 ) -> AsyncGenerator[str, None]:
     """Stream GeoJSON features from the Redis cache (cache-hit path)."""
@@ -288,6 +287,19 @@ async def _stream_from_cache(
         "cached": True,
     }) + "\n"
 
+    # Resolve decision IDs (deferred to after metadata is sent)
+    disliked_ids: set[int] | None = None
+    liked_ids: set[int] | None = None
+    if decision_filter != "everything" and user_email:
+        user_id = _get_user_id_safe(user_email)
+        if user_id is not None:
+            decision_repo = DecisionRepository(engine)
+            listing_type_str = query_parameters.listing_type.value
+            if decision_filter == "liked":
+                liked_ids = decision_service.get_liked_ids(decision_repo, user_id, listing_type_str)
+            else:
+                disliked_ids = decision_service.get_disliked_ids(decision_repo, user_id, listing_type_str)
+
     count = 0
     is_first_batch = True
     for feature_batch in get_cached_features(query_parameters, batch_size=batch_size):
@@ -337,8 +349,7 @@ async def _stream_from_db(
     limit: int | None,
     poi_distances_lookup: dict[int, list[dict[str, str | int]]] | None = None,
     skip_cache: bool = False,
-    disliked_ids: set[int] | None = None,
+    user_email: str | None = None,
-    liked_ids: set[int] | None = None,
     decision_filter: str = "all",
 ) -> AsyncGenerator[str, None]:
     """Stream GeoJSON features from the database, populating the cache as we go."""
@@ -354,6 +365,19 @@ async def _stream_from_db(
         "cached": False,
     }) + "\n"
 
+    # Resolve decision IDs (deferred to after metadata is sent)
+    disliked_ids: set[int] | None = None
+    liked_ids: set[int] | None = None
+    if decision_filter != "everything" and user_email:
+        user_id = _get_user_id_safe(user_email)
+        if user_id is not None:
+            decision_repo = DecisionRepository(engine)
+            listing_type_str = query_parameters.listing_type.value
+            if decision_filter == "liked":
+                liked_ids = decision_service.get_liked_ids(decision_repo, user_id, listing_type_str)
+            else:
+                disliked_ids = decision_service.get_disliked_ids(decision_repo, user_id, listing_type_str)
+
     staging_key: str | None = None
     if not skip_cache:
         staging_key = begin_cache_population(query_parameters)
@@ -435,31 +459,12 @@ async def stream_listing_geojson(
     # Build POI distances lookup if requested
     poi_distances_lookup = _build_poi_distances_lookup(user.email, query_parameters.listing_type) if include_poi_distances else None
 
-    # Build decision filter sets
-    disliked_ids: set[int] | None = None
-    liked_ids: set[int] | None = None
-    if decision_filter != "everything":
-        user_id = _get_user_id_safe(user.email)
-        if user_id is not None:
-            decision_repo = DecisionRepository(engine)
-            listing_type_str = query_parameters.listing_type.value
-            if decision_filter == "liked":
-                liked_ids = decision_service.get_liked_ids(
-                    decision_repo, user_id, listing_type_str
-                )
-            else:
-                # default "all": load disliked to exclude
-                disliked_ids = decision_service.get_disliked_ids(
-                    decision_repo, user_id, listing_type_str
-                )
-
     cached_count = get_cached_count(query_parameters)
     if cached_count is not None and cached_count > 0 and not include_poi_distances:
         app_metrics.geojson_cache_operations.add(1, {"result": "hit"})
         generator = _stream_from_cache(
             query_parameters, batch_size, limit,
-            disliked_ids=disliked_ids,
+            user_email=user.email,
-            liked_ids=liked_ids,
             decision_filter=decision_filter,
         )
     else:
@@ -467,8 +472,7 @@ async def stream_listing_geojson(
         generator = _stream_from_db(
             query_parameters, batch_size, limit, poi_distances_lookup,
             skip_cache=include_poi_distances,
-            disliked_ids=disliked_ids,
+            user_email=user.email,
-            liked_ids=liked_ids,
             decision_filter=decision_filter,
         )
 

tests/test_listing_geojson.py

@@ -315,3 +315,44 @@ class TestStreamingEndpoint:
         from api.app import FIRST_BATCH_SIZE
         assert len(batch_messages[0]["features"]) <= FIRST_BATCH_SIZE
 
+    def test_streaming_still_filters_disliked(self, client):
+        """Test that disliked listings are filtered even with deferred decision loading."""
+        with patch("api.app.get_cached_count", return_value=None), \
+             patch("api.app._get_user_id_safe", return_value=42), \
+             patch("api.app.ListingRepository") as MockRepo, \
+             patch("api.app.DecisionRepository"), \
+             patch("api.app.decision_service") as mock_ds:
+
+            mock_ds.get_disliked_ids.return_value = {2}
+
+            mock_instance = MagicMock()
+            mock_instance.count_listings.return_value = 2
+            mock_instance.stream_listings_optimized.return_value = iter([
+                {
+                    'id': 1, 'price': 2000.0, 'number_of_bedrooms': 2,
+                    'square_meters': 50.0, 'longitude': -0.1, 'latitude': 51.5,
+                    'photo_thumbnail': None, 'last_seen': datetime.now(),
+                    'agency': None, 'price_history_json': '[]', 'available_from': None,
+                },
+                {
+                    'id': 2, 'price': 2500.0, 'number_of_bedrooms': 2,
+                    'square_meters': 60.0, 'longitude': -0.12, 'latitude': 51.51,
+                    'photo_thumbnail': None, 'last_seen': datetime.now(),
+                    'agency': None, 'price_history_json': '[]', 'available_from': None,
+                },
+            ])
+            MockRepo.return_value = mock_instance
+
+            response = client.get("/api/listing_geojson/stream?listing_type=RENT&limit=10")
+            messages = [json.loads(line) for line in response.text.strip().split("\n")]
+
+            all_features = []
+            for m in messages:
+                if m["type"] == "batch":
+                    all_features.extend(m["features"])
+
+            feature_ids = [f["properties"]["id"] for f in all_features]
+            assert 2 not in feature_ids
+            assert 1 in feature_ids
+
+