SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '668f1d0350c74f8033cf5e462f1614e34b7598a3133296d504fd113b1dd4e515' 
  AND token = 'jf69pBRQbsUma8rDnhFJfWarIJbL69G+qCCswVqqzs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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