total traffic usage of lightsails

Amazon CloudWatch is a great tool to monitor your AWS Lightsail instances. By viewing the "NetworkIn" and "NetworkOut" CloudWatch metrics, you can get a basic idea of how much network traffic your Lightsail instance is sending and receiving over time. This blog is tailored to memory metrics, but you should be able to adpat it for network traffic metrics. https://aws.amazon.com/blogs/compute/monitoring-memory-usage-lightsail-instance/

And as per the documentation: Every single Lightsail plan also includes a healthy amount of free IN and OUT data transfer. For example, using the cheapest Lightsail instance bundle you can send and receive up to 1 TB of data to the Internet within the month, at no extra charge.

Any type of data transfer you consume is covered by your Lightsail plan and counted towards your data transfer allowance. As long as your instance’s data transfer is below the plan allowance, you do not incur any data transfer charges. Your data transfer allowance will reset every month, and you can consume it whenever you need within the month. If you delete your instance before the month ends and create another one, data transfer allowance is shared between the two instances.

https://aws.amazon.com/lightsail/faq/

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Lightsail provide NetworkIn/NetworkOut metrics for each Lightsail instance, you can find full list of metrics Lightsail provided from this doc https://lightsail.aws.amazon.com/ls/docs/en_us/articles/amazon-lightsail-resource-health-metrics, you can view the metrics from Lightsail console, under instance details page metrics tab. you can also view the metrics using lightsail cli https://docs.aws.amazon.com/cli/latest/reference/lightsail/get-instance-metric-data.html