when do you start thinking about a load balancer? like, dont wait until your site is crawling.

hey everyone, just curious about your experiences with load balancers. I've been working on a few apps that are starting to see some decent traffic, and I'm wondering when it's the right time to introduce a load balancer. Is it purely based on traffic volume, or are there other factors like redundancy, scaling needs, or even specific application architectures that make you say 'okay, time for a load balancer'?