diff --git a/pkg/migrations/apidb/11_add_user_token_balances_indexes.go b/pkg/migrations/apidb/11_add_user_token_balances_indexes.go
new file mode 100644
index 0000000..21abffb
--- /dev/null
+++ b/pkg/migrations/apidb/11_add_user_token_balances_indexes.go
@@ -0,0 +1,53 @@
+package apidb
+
+import (
+	"context"
+	"log"
+
+	reconcilerstore "github.com/chainsafe/canton-middleware/pkg/reconciler/store"
+
+	"github.com/uptrace/bun"
+)
+
+// utbIndex describes a composite unique index on user_token_balances.
+type utbIndex struct {
+	name    string
+	columns []string
+}
+
+var utbIndexes = []utbIndex{
+	{"idx_utb_fingerprint_token", []string{"fingerprint", "token_symbol"}},
+	{"idx_utb_evm_address_token", []string{"evm_address", "token_symbol"}},
+	{"idx_utb_canton_party_token", []string{"canton_party_id", "token_symbol"}},
+}
+
+func init() {
+	Migrations.MustRegister(func(ctx context.Context, db *bun.DB) error {
+		log.Println("adding unique indexes to user_token_balances...")
+
+		// These unique indexes back the ON CONFLICT upserts in reconciler/store/pg.go.
+		for _, idx := range utbIndexes {
+			if _, err := db.NewCreateIndex().
+				Model((*reconcilerstore.UserTokenBalanceDao)(nil)).
+				Index(idx.name).
+				Column(idx.columns...).
+				Unique().
+				IfNotExists().
+				Exec(ctx); err != nil {
+				return err
+			}
+		}
+		return nil
+	}, func(ctx context.Context, db *bun.DB) error {
+		log.Println("dropping unique indexes from user_token_balances...")
+		for _, idx := range utbIndexes {
+			if _, err := db.NewDropIndex().
+				Index(idx.name).
+				IfExists().
+				Exec(ctx); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}