SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91aaa471bcba3d934519eb5f38b820c6a68c76c12959ed85da7d96acb4dfd424' 
  AND token = 'JVL1E3iW6qGR0gvbXBa2rhVwo8newQbOEjhV+8QSTfQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}