SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6323978698ef1ef3bfde2e1351528171c6846546ce86d58f01c93ab16b8adffa' 
  AND token = 'h1v/TMyKOWmfjlQpEfQQvKnNyc6U1mZjPDWtxp18Ui0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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