SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '857adf6517e66fb05105c69e134f230401931cc87bd3c71f6bed4278b596c31e' 
  AND token = 'asnIE1mS9zsazdpLBlnAvpmdQIEtbhXo7RwqjEfRYjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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