diff --git a/backend/src/features/subscriptions/domain/subscriptions.service.ts b/backend/src/features/subscriptions/domain/subscriptions.service.ts
index 9e5fffe..9a31bbe 100644
--- a/backend/src/features/subscriptions/domain/subscriptions.service.ts
+++ b/backend/src/features/subscriptions/domain/subscriptions.service.ts
@@ -767,7 +767,7 @@ export class SubscriptionsService {
   ): Promise<void> {
     try {
       // Get user profile for email and name
-      const userProfile = await this.userProfileRepository.getByAuth0Sub(userId);
+      const userProfile = await this.userProfileRepository.getById(userId);
       if (!userProfile) {
         logger.warn('User profile not found for tier change notification', { userId });
         return;
@@ -925,7 +925,7 @@ export class SubscriptionsService {
 
       // Sync tier to user_profiles table (within same transaction)
       await client.query(
-        'UPDATE user_profiles SET subscription_tier = $1 WHERE auth0_sub = $2',
+        'UPDATE user_profiles SET subscription_tier = $1 WHERE id = $2',
         [newTier, userId]
       );
 
diff --git a/backend/src/features/subscriptions/jobs/grace-period.job.ts b/backend/src/features/subscriptions/jobs/grace-period.job.ts
index 60ce022..f4345b5 100644
--- a/backend/src/features/subscriptions/jobs/grace-period.job.ts
+++ b/backend/src/features/subscriptions/jobs/grace-period.job.ts
@@ -50,7 +50,7 @@ export async function processGracePeriodExpirations(): Promise<GracePeriodResult
         up.notification_email,
         up.display_name
       FROM subscriptions s
-      LEFT JOIN user_profiles up ON s.user_id = up.auth0_sub
+      LEFT JOIN user_profiles up ON s.user_id = up.id
       WHERE s.status = 'past_due'
         AND s.grace_period_end < NOW()
       ORDER BY s.grace_period_end ASC
@@ -89,13 +89,13 @@ export async function processGracePeriodExpirations(): Promise<GracePeriodResult
 
         await client.query(updateQuery, [subscription.id]);
 
-        // Sync tier to user_profiles table (user_id is auth0_sub)
+        // Sync tier to user_profiles table
         const syncQuery = `
           UPDATE user_profiles
           SET
             subscription_tier = 'free',
             updated_at = NOW()
-          WHERE auth0_sub = $1
+          WHERE id = $1
         `;
 
         await client.query(syncQuery, [subscription.user_id]);
diff --git a/backend/src/features/vehicles/domain/vehicles.service.ts b/backend/src/features/vehicles/domain/vehicles.service.ts
index e4a7f74..ca7864d 100644
--- a/backend/src/features/vehicles/domain/vehicles.service.ts
+++ b/backend/src/features/vehicles/domain/vehicles.service.ts
@@ -82,7 +82,7 @@ export class VehiclesService {
     }
 
     // Get user's tier for limit enforcement
-    const userProfile = await this.userProfileRepository.getByAuth0Sub(userId);
+    const userProfile = await this.userProfileRepository.getById(userId);
     if (!userProfile) {
       throw new Error('User profile not found');
     }
@@ -227,7 +227,7 @@ export class VehiclesService {
    */
   async getUserVehiclesWithTierStatus(userId: string): Promise<Array<VehicleResponse & { tierStatus: 'active' | 'locked' }>> {
     // Get user's subscription tier
-    const userProfile = await this.userProfileRepository.getByAuth0Sub(userId);
+    const userProfile = await this.userProfileRepository.getById(userId);
     if (!userProfile) {
       throw new Error('User profile not found');
     }