SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c15b79137b4253be244dcf4187f0547927cedde50021413c7a3fee76544642b5' 
  AND token = 'pfOCj49+GiMT/RwtWS9Pjowi+FTpvTZablNzzH0ktJk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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