SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8a289c46b2ab6dc1397a9fabb8f2232d07e5553edf6608012123a7c4cf63198' 
  AND token = 'bRrRnJahYiQUTCeYatCmtc3mGsEPkMIk5gtgBA4btIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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