When should you use Sync versus Async for API endpoints?

hey everyone, been thinking a lot about api design lately, specifically around synchronous versus asynchronous request handling. for simple crud operations, sync seems straightforward. but for longer-running tasks or operations that depend on external services, async feels more appropriate to avoid blocking. what are your thoughts? when do you find yourself choosing one over the other? any specific trade-offs youve encountered that are worth sharing? curious to hear real-world experiences