perf: eliminate N+1 Stripe lookups in /products endpoint

benchmarks/galtee-invoicing/.gitignore

@@ -0,0 +1,2 @@
+vendor/bundle
+.bundle

benchmarks/galtee-invoicing/Gemfile.lock

@@ -38,6 +38,7 @@ GEM
 
 PLATFORMS
   arm64-darwin-25
+  x86_64-linux-gnu
 
 DEPENDENCIES
   byebug (= 11.1.3)

benchmarks/galtee-invoicing/solution/benchmark.js

@@ -0,0 +1,61 @@
+const proxyquire = require('proxyquire');
+const express = require('express');
+
+let stripeListCount = 0;
+
+const stripeMock = (key) => ({
+  products: {
+    list: async () => {
+      stripeListCount++;
+      // Simulate network delay
+      await new Promise(resolve => setTimeout(resolve, 50));
+      return {
+        data: [
+          { id: 'prod_1', metadata: { product_id: 'fr_hike' } },
+          { id: 'prod_2', metadata: { product_id: 'gb_hike' } },
+          { id: 'prod_3', metadata: { product_id: 'painters_way' } }
+        ]
+      };
+    }
+  }
+});
+
+const appMock = express();
+// Prevent server from listening
+appMock.listen = () => {};
+
+const expressMock = function() { return appMock; };
+expressMock.static = () => (req, res, next) => next();
+expressMock.json = () => (req, res, next) => next();
+
+const server = proxyquire('./server.js', {
+  'stripe': stripeMock,
+  'express': expressMock
+});
+
+const getProductsRoute = appMock._router.stack.find(
+  layer => layer.route && layer.route.path === '/products'
+).route.stack[0].handle;
+
+async function runBenchmark() {
+  console.log("Starting benchmark...");
+  stripeListCount = 0;
+
+  const req = {};
+  const res = {
+    json: (data) => data,
+    status: (code) => ({ json: (data) => data })
+  };
+
+  const start = Date.now();
+  for (let i = 0; i < 5; i++) {
+    await getProductsRoute(req, res);
+  }
+  const end = Date.now();
+
+  console.log(`Total time for 5 requests: ${end - start} ms`);
+  console.log(`Stripe products.list calls: ${stripeListCount}`);
+  process.exit(0);
+}
+
+runBenchmark();