diff --git a/api/google-sheets.js b/api/google-sheets.js
new file mode 100644
index 0000000..f9a13c6
--- /dev/null
+++ b/api/google-sheets.js
@@ -0,0 +1,120 @@
+// Google Sheets sync helper
+// Non-blocking secondary write for team access and redundancy
+// Reads credentials from file (GOOGLE_SERVICE_ACCOUNT_FILE) or env var (GOOGLE_SERVICE_ACCOUNT)
+
+const fs = require('fs');
+
+let sheetsClient = null;
+let authClient = null;
+
+function getCredentials() {
+  if (!process.env.GOOGLE_SHEET_ID) return null;
+
+  // Prefer file-based credentials (cleaner for Docker)
+  const filePath = process.env.GOOGLE_SERVICE_ACCOUNT_FILE;
+  if (filePath) {
+    try {
+      return JSON.parse(fs.readFileSync(filePath, 'utf8'));
+    } catch (err) {
+      console.error('[Google Sheets] Failed to read credentials file:', err.message);
+      return null;
+    }
+  }
+
+  // Fall back to JSON string in env var
+  const raw = process.env.GOOGLE_SERVICE_ACCOUNT;
+  if (!raw) return null;
+  try {
+    return JSON.parse(raw.trim());
+  } catch {
+    console.error('[Google Sheets] Failed to parse service account JSON');
+    return null;
+  }
+}
+
+async function getSheetsClient() {
+  if (sheetsClient) return sheetsClient;
+
+  const creds = getCredentials();
+  if (!creds) return null;
+
+  const { google } = require('googleapis');
+  authClient = new google.auth.GoogleAuth({
+    credentials: creds,
+    scopes: ['https://www.googleapis.com/auth/spreadsheets'],
+  });
+  sheetsClient = google.sheets({ version: 'v4', auth: authClient });
+  return sheetsClient;
+}
+
+/**
+ * Append a row to a specific sheet tab.
+ * Non-blocking — logs errors but never throws.
+ */
+async function appendRow(sheetName, values) {
+  try {
+    const sheets = await getSheetsClient();
+    if (!sheets) {
+      console.log('[Google Sheets] Skipping sync — no credentials configured');
+      return;
+    }
+
+    await sheets.spreadsheets.values.append({
+      spreadsheetId: process.env.GOOGLE_SHEET_ID,
+      range: `${sheetName}!A:Z`,
+      valueInputOption: 'USER_ENTERED',
+      insertDataOption: 'INSERT_ROWS',
+      resource: { values: [values] },
+    });
+
+    console.log(`[Google Sheets] Synced row to "${sheetName}"`);
+  } catch (error) {
+    console.error(`[Google Sheets] Failed to sync to "${sheetName}":`, error.message);
+  }
+}
+
+/**
+ * Sync a waitlist signup to the "Waitlist" sheet tab.
+ * Columns: Timestamp | Email | Name | Involvement
+ */
+function syncWaitlistSignup({ email, name, involvement }) {
+  // Fire and forget — don't await in the request handler
+  appendRow('Waitlist', [
+    new Date().toISOString(),
+    email,
+    name,
+    involvement || '',
+  ]);
+}
+
+/**
+ * Sync an application to the "Applications" sheet tab.
+ * Columns: Timestamp | App ID | Status | First Name | Last Name | Email | Phone |
+ *          Country | City | Attendance | Motivation | Contribution | How Heard |
+ *          Referral | Scholarship | Scholarship Reason | Weeks/Dates
+ */
+function syncApplication(app) {
+  appendRow('Applications', [
+    new Date().toISOString(),
+    app.id || '',
+    'pending',
+    app.first_name || '',
+    app.last_name || '',
+    app.email || '',
+    app.phone || '',
+    app.country || '',
+    app.city || '',
+    app.attendance_type || '',
+    app.motivation || '',
+    app.contribution || '',
+    app.how_heard || '',
+    app.referral_name || '',
+    app.scholarship_needed ? 'Yes' : 'No',
+    app.scholarship_reason || '',
+    app.arrival_date && app.departure_date
+      ? `${app.arrival_date} to ${app.departure_date}`
+      : '',
+  ]);
+}
+
+module.exports = { syncWaitlistSignup, syncApplication };