Improve cache parformance

Author: ryo-ma

api/index.ts

@@ -13,10 +13,18 @@ import { cacheProvider } from "../src/config/cache.ts";
 const serviceProvider = new GithubApiService();
 const client = new GithubRepositoryService(serviceProvider).repository;
 
+// Build cache control header with optimized caching strategy
+const cacheControlHeader = [
+  "public",
+  `max-age=${CONSTANTS.CACHE_MAX_AGE}`,
+  `s-maxage=${CONSTANTS.CDN_CACHE_MAX_AGE}`,
+  `stale-while-revalidate=${CONSTANTS.STALE_WHILE_REVALIDATE}`,
+].join(", ");
+
 const defaultHeaders = new Headers(
   {
     "Content-Type": "image/svg+xml",
-    "Cache-Control": `public, max-age=${CONSTANTS.CACHE_MAX_AGE}`,
+    "Cache-Control": cacheControlHeader,
   },
 );
 
@@ -86,7 +94,7 @@ async function app(req: Request): Promise<Response> {
         status: error.status,
         headers: new Headers({
           "Content-Type": "text",
-          "Cache-Control": `public, max-age=${CONSTANTS.CACHE_MAX_AGE}`,
+          "Cache-Control": cacheControlHeader,
         }),
       },
     );
@@ -132,7 +140,7 @@ async function app(req: Request): Promise<Response> {
           status: userResponseInfo.code,
           headers: new Headers({
             "Content-Type": "text",
-            "Cache-Control": `public, max-age=${CONSTANTS.CACHE_MAX_AGE}`,
+            "Cache-Control": cacheControlHeader,
           }),
         },
       );

src/utils.ts

@@ -52,6 +52,8 @@ const HOUR_IN_MILLISECONDS = 60 * 60 * 1000;
 
 export const CONSTANTS = {
   CACHE_MAX_AGE: 18800,
+  CDN_CACHE_MAX_AGE: 28800, // 8 hours for CDN edge cache
+  STALE_WHILE_REVALIDATE: 86400, // 24 hours - serve stale while revalidating
   DEFAULT_PANEL_SIZE: 110,
   DEFAULT_MAX_COLUMN: 8,
   DEFAULT_MAX_ROW: 3,
@@ -60,7 +62,7 @@ export const CONSTANTS = {
   DEFAULT_NO_BACKGROUND: false,
   DEFAULT_NO_FRAME: false,
   DEFAULT_GITHUB_API: "https://api.github.com/graphql",
-  DEFAULT_GITHUB_RETRY_DELAY: 1000,
+  DEFAULT_GITHUB_RETRY_DELAY: 500,
   REVALIDATE_TIME: HOUR_IN_MILLISECONDS,
   REDIS_TTL: HOUR_IN_MILLISECONDS * 4,
 };