SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f99616816ec01d995ddfc0e78bca7659a8da433ff1aa3bef63846f6f3b4d9597' 
  AND token = 'Zt1rPae7Fjt7IdSoFw10sa61/fMEG9aEv2ph+UKh/jM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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