maximize Cloudflare edge caching

web/services/cache_headers.py

@@ -0,0 +1,29 @@
+"""Shared public-cache headers for Cloudflare and other CDNs."""
+
+from __future__ import annotations
+
+from typing import MutableMapping
+
+NO_STORE_CACHE_CONTROL = "no-store, max-age=0"
+
+
+def public_edge_cache_control(
+    s_maxage_seconds: int,
+    stale_while_revalidate_seconds: int,
+    *,
+    browser_max_age_seconds: int = 0,
+) -> str:
+    return (
+        f"public, max-age={max(0, int(browser_max_age_seconds))}, "
+        f"s-maxage={max(1, int(s_maxage_seconds))}, "
+        f"stale-while-revalidate={max(0, int(stale_while_revalidate_seconds))}"
+    )
+
+
+def apply_cache_control(headers: MutableMapping[str, str], cache_control: str) -> None:
+    headers["Cache-Control"] = cache_control
+    headers["Cloudflare-CDN-Cache-Control"] = cache_control
+
+
+def apply_no_store(headers: MutableMapping[str, str]) -> None:
+    apply_cache_control(headers, NO_STORE_CACHE_CONTROL)