So, when do you actually need a database replica?

Hey everyone, I've been thinking about database scalability lately. We're doing alright with our single primary instance, but I'm starting to see some read contention during peak hours. I know read replicas are a common solution, but when is the tipping point where the complexity of managing replicas outweighs the benefits? Are there specific metrics or query patterns that signal it's time to move beyond a single instance? What are your experiences with setting up and maintaining read replicas?