There are plenty of use cases when you need to take certain actions when an instance is launched. Say for example, you need to tag instances to follow standards, and for billing purposes, or perhaps call an external API to notify a custom monitoring tool, or inventory tracking application. In other words, there are events that you want to trigger off auto scaling, but don't necessarily need to occur during the startup sequence or termination of your instance. They can occur a few seconds early or late, without any significant impact. In this case, a better choice would be to use event bridge as an alternative to auto scaling lifecycle hooks. This diagram illustrates the idea behind this option. Event bridge gets notified of all auto scaling activities in your account, and it's your job to identify the auto scaling group that you're interested in, by filtering events.

Once you do this, you'll get notified of scale-in and scale-out events, which you can then use to trigger actions. In this case, we can create an AWS lambda function, and perform our desired actions, which could include; EC2 fleet to fleet tracking, notifications, third party tags, and many more. The key to remember here is that all this can occur, decouple from your EC2 instances. If you needed something to occur within your instance at a specific time, such as startup or termination, then this idea wouldn't work, and the lifecycle hook is the appropriate choice. Here's a link for the AWS documentation, regarding auto scaling and event bridge.