CDN edge caching for APIs: how aggressive can you be?

we have a public product catalog api handling about 100k requests per minute, and the underlying data changes around 100 times a day. we're trying to push as much caching as possible to the cdn edge to reduce origin load and improve latency for global users. the challenge is how aggressive we can actually be. we have authenticated and unauthenticated endpoints, and some responses are personalized. cache key design is complex to handle variations like query parameters and headers. purging stale data from the cdn can also be tricky and slow. what's your experience with aggressive cdn edge caching for apis, especially when dealing with authenticated requests, varying response content, and data that changes moderately frequently? what techniques have you used to maximize cache hit rates while maintaining data freshness and correctness?