What do cold starts generally occur due to?

Cold starts generally occur due to long idle periods for the function. When a serverless function, such as an AWS Lambda function, is not invoked for a certain period, the platform may scale down and remove the function's execution environment to free up resources. This gives rise to a "cold start" when the function is invoked again after a lengthy period of inactivity, as the cloud provider then needs to initialize a new environment, resulting in added latency.

Long idle periods lead to this scenario because the platform is designed to optimize resource utilization by not keeping infrequently used functions "warm." This process contrasts with functions that are invoked regularly, where the execution environment can be reused, minimizing latency. Therefore, understanding that cold starts are primarily linked to the periods of inactivity helps in both application design and performance optimization for serverless architectures.