How to check Bitcoin wallet balance without any API I am building an application and that will involve large set of bitcoin wallets and need to keep on checking for balance. I don't want to use any third party APIs as they all have hourly/secondly limits.

Is there any way I can check bitcoin wallets balance without any API? I am not sure is Bitcoin Demon and Bitcoin Core is for this purpose. Can anyone please suggest me the best way to verify bitcoin balances and transactions without any limits.
If you are not going to use a 3rd party API, you'll need to run a node and add each address you want to query as a watch only address. If you are looking to create a database with all addresses, similar to a block explorer website, you'll need to parse the blockchain using something like abe, and then continually update your database for each new transaction.  There's also the painful approach of turning on txindex=1 in your bitcoin.conf, and then going through every single block since genesis, that checks all txs outputs and then keeps a record of all addresses and transactions.