Optimize dashboard overview loading

api/main.py

@@ -1,5 +1,6 @@
 import hashlib
 import os
+import time
 from contextlib import asynccontextmanager
 
 from fastapi import FastAPI
@@ -26,26 +27,37 @@ class ETagMiddleware(BaseHTTPMiddleware):
     """Add ETag + conditional-GET (304) support to all JSON GET responses."""
 
     async def dispatch(self, request: Request, call_next):
+        started = time.perf_counter()
         response = await call_next(request)
         if request.method != "GET":
+            response.headers["X-StateHub-Elapsed-Ms"] = f"{(time.perf_counter() - started) * 1000:.1f}"
             return response
         if "application/json" not in response.headers.get("content-type", ""):
+            response.headers["X-StateHub-Elapsed-Ms"] = f"{(time.perf_counter() - started) * 1000:.1f}"
             return response
 
         body_parts = []
         async for chunk in response.body_iterator:
             body_parts.append(chunk)
         body = b"".join(body_parts)
+        elapsed_ms = f"{(time.perf_counter() - started) * 1000:.1f}"
 
         etag = '"' + hashlib.md5(body, usedforsecurity=False).hexdigest() + '"'
         if request.headers.get("if-none-match") == etag:
             return StarletteResponse(
                 status_code=304,
-                headers={"ETag": etag, "Cache-Control": "no-cache"},
+                headers={
+                    "ETag": etag,
+                    "Cache-Control": "no-cache",
+                    "X-StateHub-Elapsed-Ms": elapsed_ms,
+                    "X-StateHub-Response-Bytes": "0",
+                },
             )
 
         headers = {k: v for k, v in response.headers.items() if k.lower() != "content-length"}
         headers["ETag"] = etag
+        headers["X-StateHub-Elapsed-Ms"] = elapsed_ms
+        headers["X-StateHub-Response-Bytes"] = str(len(body))
         if not any(k.lower() == "cache-control" for k in headers):
             headers["Cache-Control"] = "no-cache"
         return StarletteResponse(
@@ -84,7 +96,7 @@ app.add_middleware(
     allow_origins=_cors_origins,
     allow_methods=["GET", "POST", "PATCH", "DELETE", "PUT"],
     allow_headers=["Content-Type", "If-None-Match"],
-    expose_headers=["ETag"],
+    expose_headers=["ETag", "X-StateHub-Elapsed-Ms", "X-StateHub-Response-Bytes", "X-StateHub-Cache"],
 )
 
 app.include_router(domains.router)