How do you handle rate limiting in your SaaS or API?

I’ve been building APIs for a while, and one of the recurring headaches is rate limiting. Most tools are either too rigid, too slow, or don’t let you limit on custom criteria (like by user ID, API key, or plan).

Curious how others here are solving it:

• Do you roll your own logic?

• Use a library/service?

• Or just hope traffic won’t spike? 😅

I’d love to hear your stories (and horror stories). Always interesting to see how different teams handle this.