Caching: when is it prob more trouble than its worth

hey everyone, been thinking a lot about caching lately. weve got several services that could benefit from it, but im also seeing the potential for cache invalidation headaches down the line. were talking about user session data, frequently accessed product catalogs, that sort of thing. what are your experiences? when have you found that the complexity of managing a cache, especially ensuring data consistency across different layers or services, outweighs the performance gains? are there specific thresholds or patterns that make you say 'nope, not worth it'?