Add out of bounds fetching

server/config.py

@@ -12,6 +12,10 @@ from pipeline.config import (
     DEFAULT_MAX_PRICE,
 )
 
+# Extra area to return beyond requested bounds (0.2 = 20%)
+# Makes panning smoother by preloading nearby hexagons
+BOUNDS_BUFFER_PERCENT = 0.2
+
 __all__ = [
     "AGGREGATES_DIR",
     "VALID_RESOLUTIONS",
@@ -22,4 +26,5 @@ __all__ = [
     "DEFAULT_MAX_YEAR",
     "DEFAULT_MIN_PRICE",
     "DEFAULT_MAX_PRICE",
+    "BOUNDS_BUFFER_PERCENT",
 ]

server/routes/hexagons.py

@@ -14,6 +14,7 @@ from server.config import (
     DEFAULT_MAX_YEAR,
     DEFAULT_MIN_PRICE,
     DEFAULT_MAX_PRICE,
+    BOUNDS_BUFFER_PERCENT,
 )
 
 router = APIRouter()
@@ -138,6 +139,16 @@ async def get_hexagons(
             status_code=400, detail="Invalid bounds format. Use: south,west,north,east"
         )
 
+    # Expand bounds by buffer percentage for smoother panning
+    lat_range = north - south
+    lng_range = east - west
+    lat_buffer = lat_range * BOUNDS_BUFFER_PERCENT
+    lng_buffer = lng_range * BOUNDS_BUFFER_PERCENT
+    south -= lat_buffer
+    north += lat_buffer
+    west -= lng_buffer
+    east += lng_buffer
+
     # Round bounds to reduce cache misses (0.01 degree ≈ 1km precision)
     # Always expand bounds (floor for min, ceil for max) to prevent hexagons
     # popping in when crossing rounding boundaries