diff --git a/backend/prisma/migrations/20260830000000_add_webhook_overdue_invoice_indexes/migration.sql b/backend/prisma/migrations/20260830000000_add_webhook_overdue_invoice_indexes/migration.sql
new file mode 100644
index 0000000..4fc00f1
--- /dev/null
+++ b/backend/prisma/migrations/20260830000000_add_webhook_overdue_invoice_indexes/migration.sql
@@ -0,0 +1,12 @@
+-- Add missing database indexes for the webhook queue, overdue sweep, and
+-- merchant invoice list queries.
+
+-- Webhook queue: the worker polls pending deliveries whose next attempt is due.
+CREATE INDEX "webhook_deliveries_status_next_attempt_at_idx" ON "webhook_deliveries"("status", "next_attempt_at");
+
+-- Overdue sweep: the daily cron marks pending invoices past their due date as overdue.
+CREATE INDEX "invoices_status_due_date_idx" ON "invoices"("status", "due_date");
+
+-- Merchant invoice list: the dashboard lists a merchant's non-draft invoices by
+-- status, ordered by creation date.
+CREATE INDEX "invoices_merchant_id_is_draft_status_created_at_idx" ON "invoices"("merchant_id", "is_draft", "status", "created_at");
diff --git a/backend/prisma/schema.prisma b/backend/prisma/schema.prisma
index 45b2042..4e133bd 100644
--- a/backend/prisma/schema.prisma
+++ b/backend/prisma/schema.prisma
@@ -128,6 +128,7 @@ model WebhookDelivery {
   createdAt      DateTime       @default(now()) @map("created_at")
   updatedAt      DateTime       @updatedAt @map("updated_at")
 
+  @@index([status, nextAttemptAt])
   @@map("webhook_deliveries")
 }
 
@@ -246,6 +247,8 @@ model Invoice {
   @@index([merchantId])
   @@index([isDraft, merchantId])
   @@index([lastAutoSavedAt])
+  @@index([status, dueDate])
+  @@index([merchantId, isDraft, status, createdAt])
   @@map("invoices")
 }