If you want to get information when a certain event happens on the Blockchain, you need to setup your own node for each blockchain and each network, write your own logic and spend a lot of time and money.
The other option is to use Blockchain Webhooks where you can request a callback notification for certain events, you will get the callback only when this event happens.
Using Webhooks looks much better, faster, and cheaper but the question is how to find the best such service on the market, there are few already but which one is really stable and scalable.
Crypto APIs Webhooks 2.0 is stable and scalable, fast, and you will never miss a notification.
The stress tests we made showed that we can monitor +1B addresses for a single blockchain network without any delay or missing notifications.
Webhooks for Bitcoin as an example: https://docs.cryptoapis.io/rest-apis/blockchain-as-a-service-apis/btc/index#webhook-notifications