diff --git a/lib/app.js b/lib/app.js
index e2455b63a..b5140657c 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -127,23 +127,38 @@ const start = async () => {
   }
 };
 
-// Shut down the server
+const FORCE_SHUTDOWN_TIMEOUT_MS = 5000;
+
+/**
+ * Gracefully shut down the server, disconnecting services before exiting.
+ * If the server promise rejects (e.g. failed to start), logs the error and exits.
+ * A forced exit is triggered after {@link FORCE_SHUTDOWN_TIMEOUT_MS} ms if shutdown hangs.
+ *
+ * @param {Promise<{http: import('http').Server}>} server - Promise returned by {@link start}
+ * @returns {Promise<void>} Resolves when shutdown is initiated (process exits via callback)
+ */
 const shutdown = async (server) => {
+  // Force exit if graceful shutdown hangs
+  const forceTimeout = setTimeout(() => {
+    console.error(chalk.red('Forced shutdown (timeout)'));
+    process.exit(1);
+  }, FORCE_SHUTDOWN_TIMEOUT_MS);
+  forceTimeout.unref();
+
   try {
-    server.then(async (value) => {
-      await mongooseService.disconnect();
-      // add sequelize
-      value.http.close((err) => {
-        console.info(chalk.yellow('Server closed'));
-        if (err) {
-          console.info(chalk.red('Error on server close.', err));
-          process.exitCode = 1;
-        }
-        process.exit();
-      });
+    const value = await server;
+    await mongooseService.disconnect();
+    value.http.close((err) => {
+      console.info(chalk.yellow('Server closed'));
+      if (err) {
+        console.info(chalk.red('Error on server close.', err));
+        process.exitCode = 1;
+      }
+      process.exit();
     });
-  } catch (e) {
-    throw new Error(e);
+  } catch (err) {
+    console.error(chalk.red('Shutdown error: server never started or shutdown failed'), err);
+    process.exit(1);
   }
 };
 
diff --git a/modules/billing/README.md b/modules/billing/README.md
new file mode 100644
index 000000000..08a709ef2
--- /dev/null
+++ b/modules/billing/README.md
@@ -0,0 +1,63 @@
+# Billing Module
+
+Stripe-based billing with per-plan quota management.
+
+## Quota System
+
+### Configuration
+
+Each downstream project defines its quotas in the billing config:
+
+```js
+// config/defaults/development.config.js
+billing: {
+  quotas: {
+    free:    { documents: { create: 10, export: 50 } },
+    starter: { documents: { create: 100, export: 500 } },
+    pro:     { documents: { create: Infinity, export: Infinity } },
+  },
+}
+```
+
+### Middleware — `requireQuota(resource, action)`
+
+Enforces per-plan limits on routes. Returns 429 when quota exceeded.
+
+```js
+import requireQuota from '../billing/middlewares/billing.requireQuota.js';
+
+app.route('/api/documents')
+  .post(passport.authenticate('jwt', { session: false }),
+    organization.resolveOrganization,
+    requireQuota('documents', 'create'),
+    documents.create);
+```
+
+### Tracking Usage — `BillingUsageService`
+
+Increment counters after successful operations:
+
+```js
+import BillingUsageService from '../billing/services/billing.usage.service.js';
+
+// After creating a document
+await BillingUsageService.increment(organizationId, 'documents.create', 1);
+```
+
+### Usage Endpoint
+
+`GET /api/billing/usage` — returns current usage, limits, and plan for the authenticated org.
+
+### Events
+
+Listen for plan changes in downstream modules:
+
+```js
+import { billingEvents } from '../billing/lib/events.js';
+
+billingEvents.on('plan.changed', ({ organizationId, previousPlan, newPlan, isDowngrade }) => {
+  if (isDowngrade) {
+    // Handle downgrade (e.g. disable premium features)
+  }
+});
+```
diff --git a/modules/billing/config/billing.development.config.js b/modules/billing/config/billing.development.config.js
index f7e3ac0a1..3451eaf79 100644
--- a/modules/billing/config/billing.development.config.js
+++ b/modules/billing/config/billing.development.config.js
@@ -2,6 +2,12 @@ const config = {
   billing: {
     // Plans available for subscriptions — extend as needed
     plans: ['free', 'starter', 'pro', 'enterprise'],
+    // Quotas — downstream projects override these per plan:
+    // quotas: {
+    //   free:    { documents: { create: 10, export: 50 } },
+    //   starter: { documents: { create: 100, export: 500 } },
+    //   pro:     { documents: { create: Infinity, export: Infinity } },
+    // },
     // Stripe subscription statuses — see https://docs.stripe.com/api/subscriptions/object#subscription_object-status
     statuses: [
       'incomplete',