Fetch UTXO Bitcoin to address created by rpc importprivkey without rescan like other api
Because these api are very fast response, I think they're not using rescan.


No, they maintain massive databases that index every transaction and transaction output and their associated addresses. Bitcoin Core does not need this for normal function, and the vast majority of users do not need access to such information. Bitcoin Core does not and cannot build such databases.


  I'm using version 0.16


Then there is nothing you can do.

If you were using 0.18, then you could use the scantxoutset command to just scan the UTXO set for UTXOs. This is very quick, and you can specify multiple addresses to do it as single batch scan. scantxoutset will give you all of the UTXOs for the specified addresses but will not add them to any wallets loaded in Bitcoin Core. However, it does not sound like you are using the wallet so that should be fine.