API integrations usually feel easy at the beginning. A few requests, some authentications, maybe a webhook or two and everything works fine. Then your app grows; more users, more traffic, more concurrent requests, more dependencies. That's when things start breaking.

1. Rate limits hit faster than expected

What worked for 50 users suddenly fails at 5000.

Without queues, batching or retry strategies, external APIs can quickly become bottlenecks.

2. Small delays become big problems