SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '76868a4722cc753ac310900c3a98da6d8364ae95909bc222d47286a774be4e10' 
  AND token = 'RBOkAhunCIP/T/iLBvcBeLyAuKTCbidpUuceXKtv+Hk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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