SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a73d8941acf0cdc566f87bc3017f96eb961a06bce6243b582c40dd769e35a8e6' 
  AND token = 'Ytg/iAjkGUgsvQiUhqj0lv2VVwZD8QGMv2wlUlTSY/M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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