How do microservices communicate — REST, gRPC, and event-driven?

Question

"Breaking monolith into 5 services. REST, gRPC, or message queues?"

Interview OS Community · Accepted Answer

| Pattern | Coupling | Latency | Best For |
|---------|----------|---------|----------|
| REST | High | ~50ms | Public APIs |
| gRPC | Medium | ~5ms | Internal, high-perf |
| Events (Kafka) | Low | ~100ms | Decoupled, resilient |

```typescript
// gRPC: Binary Protocol Buffers, 7-10x faster than REST JSON
// Events: Fire and forget, eventual consistency
await kafka.produce("order.created", { orderId });
kafka.consume("order.created", async (e) => { await processPayment(e); });
```

**Recommendation**: gRPC for synchronous needs (auth, payment), async events for fire-and-forget (notifications, analytics), REST for external APIs only.

Interview OS

How do microservices communicate — REST, gRPC, and event-driven?

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Pattern	Coupling	Latency	Best For
REST	High	~50ms	Public APIs
gRPC	Medium	~5ms	Internal, high-perf
Events (Kafka)	Low	~100ms	Decoupled, resilient