Choosing the wrong protocol creates a bottleneck. Most systems use multiple protocols for different needs.
Real-world: what big apps use
| Company | External API | Internal | Real-time |
|---|---|---|---|
| Stripe | REST + Webhooks | gRPC | SSE |
| GitHub | REST + GraphQL | gRPC | SSE |
| Netflix | REST | gRPC | WebSockets |
| Slack | REST + Webhooks | Kafka + gRPC | WebSockets |