SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f749bb7dc10145a6a28e3d82823794069ed0caf2ba12695fbef3a78c7ffffb6' 
  AND token = 'UR5WPxTQxzPd8SeSSX1jD587MS7vYvVn//6QUMaLqgU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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