SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd839c323f4a8deb145b9935f470323f62a8371cb6fdf85ce9269477db41e8e38' 
  AND token = '2mXc/kC+0znBkw78QhysGnD26w9fUpDAbLrUWej1F3M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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