diff --git a/db/workflow.go b/db/workflow.go
index 5f9d0bee2..b56f39834 100644
--- a/db/workflow.go
+++ b/db/workflow.go
@@ -33,7 +33,7 @@ var (
 
 // CreateWorkflow creates a new workflow
 func (d TinkDB) CreateWorkflow(ctx context.Context, wf Workflow, data string, id uuid.UUID) error {
-	tx, err := d.instance.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelRepeatableRead})
+	tx, err := d.instance.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelSerializable})
 	if err != nil {
 		return errors.Wrap(err, "BEGIN transaction")
 	}
diff --git a/deploy/db/tinkerbell-init.sql b/deploy/db/tinkerbell-init.sql
index f78bd3835..a0eda5203 100644
--- a/deploy/db/tinkerbell-init.sql
+++ b/deploy/db/tinkerbell-init.sql
@@ -68,6 +68,8 @@ CREATE TABLE IF NOT EXISTS workflow_worker_map (
         , worker_id UUID NOT NULL
 );
 
+CREATE UNIQUE INDEX IF NOT EXISTS uidx_workflow_worker_map ON workflow_worker_map (workflow_id, worker_id);
+
 CREATE TABLE IF NOT EXISTS workflow_data (
         workflow_id UUID NOT NULL
         , version INT