What is the cause of port conflict when scaling docker compose services?

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Port conflict can occur when scaling docker compose services if more than one instance of the same container tries to bind to the same port. This can happen when the port is hard-coded in the Dockerfile or in the docker-compose.yml file, and multiple instances try to use it at the same time. When this happens, the second container attempting to use the same port will fail to start, causing a port conflict error. To avoid this, it is recommended to use dynamic port binding or make sure each container is assigned a unique port number.