SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15e3af61453bed56c9bd96f91d7e635ca3826b728cf5a9fe90f5d461bb858925' 
  AND token = 'd4n20SlY+soOADpSA27FL/YaQMWW0qMqcVuekBTSmQE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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