TL;DR — Third-Party API Rate Limited

You run a payment processing aggregator that calls Stripe's API for charge creation, refunds, and balance queries. Your Stripe plan allows 100 requests per second. Normally, you send 60 RPS, leaving headroom. The integration is synchronous — your API endpoint calls Stripe directly and waits for the response before replying to your client. Key features: All payment requests must eventually be processed (no drops). Users get immediate feedback (accepted, queued, or rejected).