When should we think about doing things asynchronously, you know, not all at once?

ive been thinkin bout how to make our services more resilient and responsive under load. were hitting some bottlenecks w synchronous request/response patterns for background tasks like sending emails or generating reports. curious to hear from others bout their experiences. when did you start exploring async processing, and what patterns like message queues or background jobs have you found most effective for different use cases? whats the key indicators that signal its time to move away from synchronous operations