From 8a8df2ebfac48c4f3afdcde15b6fda3873bbdba1 Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Mon, 26 Jan 2026 21:30:35 +0000
Subject: [PATCH] Add out of bounds fetching

---
 server/config.py          |  5 +++++
 server/routes/hexagons.py | 11 +++++++++++
 2 files changed, 16 insertions(+)

diff --git a/server/config.py b/server/config.py
index dfc1f00..798a6bd 100644
--- a/server/config.py
+++ b/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",
 ]
diff --git a/server/routes/hexagons.py b/server/routes/hexagons.py
index b4cc24f..987c749 100644
--- a/server/routes/hexagons.py
+++ b/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