SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cb14dcacf857f8d98c0e000a559ddc60f300b4e781779dc55d51ebbd616dda76' 
  AND token = 'WCKLUNIOMWWAWAEMYCi27B0cjXsts9gJBnCiKpn+Fmo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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