Merge pull request #3735 from PolicyEngine/fix/metadata-gzip-compresslevel

Lower ASGI gzip compresslevel from 9 to 4

Author: anth-volk

changelog.d/metadata-gzip-compresslevel.fixed.md

@@ -0,0 +1 @@
+Lower the ASGI gzip compression level from 9 to 4 so large responses like /us/metadata spend seconds less CPU compressing on Cloud Run, restoring warm-latency parity with App Engine.

policyengine_api/asgi_factory.py

@@ -53,7 +53,12 @@ def create_asgi_app(wsgi_app) -> FastAPI:
         redoc_url=None,
         openapi_url=None,
     )
-    app.add_middleware(GZipMiddleware, minimum_size=1000)
+    # compresslevel 4 instead of starlette's default 9: /us/metadata is ~70MB
+    # raw, and level-9 compression inside the request costs seconds of CPU on
+    # Cloud Run (where no nginx sidecar handles gzip, unlike App Engine flex).
+    # Measured on the real payload: level 9 = 5.5s -> 9.0MB, level 4 = 0.7s ->
+    # 9.9MB — 7.5x faster for ~10% larger output.
+    app.add_middleware(GZipMiddleware, minimum_size=1000, compresslevel=4)
 
     @app.middleware("http")
     async def add_cors_for_native_routes(request, call_next):