SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ff0e8b9b742b8ce4cf9650a8dfe0fea01da2fe5ff0db73eb56359619dda874a' 
  AND token = 'jCMtVPirSEJpLewRFw5T06lkIhZFIzSYrxoRuT+IOVQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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