SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9bc6aabf06256e566980415ed4f986ae7a405a1a81bdedd407539a162491a051' 
  AND token = 'f3FmRcuVlXir6mSnywFXYXzwjI9d08y2tMWQr33D0z8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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