I'm using youtube data API at Google Cloud Console.
I want to send slack to my channel if it's quota exceed 90% of quota limit per day. (900) By setting Alert policy at Monitoring Tab
I want to know setting an alert policy and sending alert is free or paid?
At some Google monitoring document it costs by metric but I'm confused.
Setting up an alert policy and sending alerts using Google Cloud Monitoring is free. As confirmed in the documentation for both metric-based & log-based alerting policies, there are no costs associated with using alerting policies.
Cost might come from the use of notification channels such as pub/sub notification channels. For example, Custom metrics are charged based on the number of data points collected. Check Chargeable metrics and Cloud Monitoring pricing summary for more information.
In addition to that, writing a metric produces costs If it's a custom metric. Standard metrics are free of charge.
If you want to know how much a metric costs you basically have to calculate from the price, most likely with Google Cloud pricing calculator.
Important is how often the metrics get written. One example for 2000 custom metrics:
once a minute = 134 Dollar
every 30 sec = 306 Dollar
every 5 sec = 2030 Dollar