SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1a8bab80450b83899679c40425cfc51aef545a1fc937fbc84523979022a53650' 
  AND token = 'mKLITwjdiIz83QmViReAHmnV96qQ/V5s9fglZcnL5SI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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