diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index fe929da..e16e424 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -24,6 +24,10 @@ jobs:
         with:
           path: |
             _site/**/*.blurred
+            _site/**/*-320w.*
+            _site/**/*-640w.*
+            _site/**/*-1280w.*
+            _site/**/*-1920w.*
           key: ${{ runner.os }}-11ty-images-${{ hashFiles('img/**/*', 'posts/**/*.{jpg,jpeg,png,gif,webp,svg,avif}', '_includes/**/*', '_11ty/blurry-placeholder.js', '_11ty/img-dim.js', '_11ty/srcset.js', '.eleventy.js') }}
           restore-keys: |
             ${{ runner.os }}-11ty-images-
diff --git a/_11ty/optimize-html.js b/_11ty/optimize-html.js
index 197d18e..9a064ec 100644
--- a/_11ty/optimize-html.js
+++ b/_11ty/optimize-html.js
@@ -29,6 +29,16 @@ const ampOptimizer = AmpOptimizer.create({
 const PurgeCSS = require("purgecss").PurgeCSS;
 const csso = require("csso");
 
+// Cache the CSS file content at module level so it is only read once per build
+// rather than once per HTML page (can be 400+ reads otherwise).
+let _cssCache = null;
+function getCss() {
+  if (!_cssCache) {
+    _cssCache = require("fs").readFileSync("css/main.css", { encoding: "utf-8" });
+  }
+  return _cssCache;
+}
+
 /**
  * Inlines the CSS.
  * Makes font display display-optional
@@ -45,9 +55,7 @@ const purifyCss = async (rawContent, outputPath) => {
     !isAmp(content) &&
     !/data-style-override/.test(content)
   ) {
-    let before = require("fs").readFileSync("css/main.css", {
-      encoding: "utf-8",
-    });
+    let before = getCss();
 
     before = before.replace(
       /@font-face {/g,
diff --git a/_11ty/srcset.js b/_11ty/srcset.js
index 639e87b..b83883d 100644
--- a/_11ty/srcset.js
+++ b/_11ty/srcset.js
@@ -43,12 +43,19 @@ const quality = {
 
 const optionalFormats = new Set(["avif", "webp"]);
 
+// On Netlify deploy-previews and branch-deploys, skip AVIF (slowest format,
+// not needed for correctness). Locally (no CONTEXT env var) treat as production.
+const isProduction = !process.env.CONTEXT || process.env.CONTEXT === "production";
+
 function supportsOutputFormat(format) {
   const info = sharp.format[format];
   return Boolean(info && info.output);
 }
 
 module.exports = async function srcset(filename, format) {
+  if (format === "avif" && !isProduction) {
+    return null;
+  }
   if (!supportsOutputFormat(format)) {
     if (optionalFormats.has(format)) {
       return null;
@@ -84,7 +91,7 @@ async function resize(filename, width, format) {
     .resize(width)
     [format]({
       quality: quality[format] || quality.default,
-      reductionEffort: 6,
+      reductionEffort: 4,
     })
     .toFile("_site" + out);
 
diff --git a/netlify.toml b/netlify.toml
new file mode 100644
index 0000000..b3350d2
--- /dev/null
+++ b/netlify.toml
@@ -0,0 +1,15 @@
+[build]
+  command = "npm run build-ci"
+  publish = "_site"
+
+[build.environment]
+  NODE_VERSION = "18"
+
+[[plugins]]
+  package = "netlify-plugin-cache"
+
+  [plugins.inputs]
+  paths = [
+    "_site/img",
+    "_site/posts"
+  ]
diff --git a/package.json b/package.json
index a92a741..e7e616a 100644
--- a/package.json
+++ b/package.json
@@ -31,6 +31,7 @@
   },
   "devDependencies": {
     "@11ty/eleventy": "^1.0.0",
+    "netlify-plugin-cache": "^1.0.3",
     "@11ty/eleventy-navigation": "^0.1.3",
     "@11ty/eleventy-plugin-rss": "^1.0.7",
     "@11ty/eleventy-plugin-syntaxhighlight": "^3.0.1",