Too Long; Didn't Read
A serverless function is served by one or multiple micro-containers. When a request comes in, our function will check whether there is a container already running to serve the invocation. If there isn't a container readily available, the function will spin up a new one and this is what we call a "cold start" When a cold start is invoked, the request will take additional time to be completed. That's the problem with cold starts: they make our application respond slower. In the "instant-age" of the 21st century, this could be a big problem.