When should you think about using a reverse proxy?

hey folks, ive been thinking a lot about reverse proxies lately, espcially in the context of scaling and security. We use one now, but Im curious about the tipping point. At what point in an applications lifecycle or traffic load does a reverse proxy become a must-have rather than a nice-to-have? Are there specific performance metrics or architectural patterns that signal its time? Would love to hear your experiences and thoughts on when to introduce one.