When should you start thinking about caching strategies?

hey folks, i've been seeing a lot of talk about caching lately, and it got me thinking. we've all got services that are getting slammed, and caching seems like an obvious solution. but how do you know when it's time to actually implement caching? is it purely based on load, or are there other indicators? and once you decide to cache, what are the first things you should consider? like, should we be thinking about client-side, server-side, or database-level caching first? looking forward to hearing your experiences and best practices