A common one are multi-tenant applications where you want to dynamically (depending on data in a database for example) route requests to different places (like

A common one are multi-tenant applications where you want to dynamically (depending on data in a database for example) route requests to different places (like docker containers). The first specific example I can think of is JupyterHub - it handles user management and starting/stopping Jupyter Notebook servers, then provides a reverse proxy for users to access their notebook servers directly.