What Protocol to Use?

As tech lead I get this question more often the before:

“What protocol should I use?”

As software stacks keep growing, the question “Which protocol should we use?” pops up a lot. It’s a key decision during design, but it tends to matter less once the system is humming along.

If your system is already live and you’re still wrestling with this, I hope it’s because you’re adding something great—like a new integration. If not, you may be uncovering foundational issues from the early design phase. Either way, treat the question with respect and choose a protocol that’s safe, sensible, and future-proof.

Of course the answer is depends, right?

Here my goal is to help with thinking, how you can answer on your own without going into details.

I do think the best approach is to THINK this question is never ALONE.This question is rising immediatelly another question:

WHERE?

I mean you can provide correct answer yourself if you know the WHERE? part as well.

In a typical stack you need REST/GraphQL (SOAP) for the front end which is public area. But as soon the request is “in house” (backend) then you contine probably with gRPC for performance (mainly service to service). For async use NAST. And in the very back in your ecosystem may you will need even queue driven protocol like RabbitMQ and Kafka….

Decision Matrix

Protocol	Speed	Complexity	Use Case
gRPC	⚡⚡⚡	Medium	Internal services, performance critical
REST	⚡⚡	Low	Public APIs, simple CRUD
NATS	⚡⚡⚡	Medium	Events, pub/sub, fire-and-forget
Kafka	⚡⚡⚡	High	Event streaming, analytics
RabbitMQ	⚡⚡	Medium	Task queues, reliable messaging
GraphQL	⚡⚡	Medium	Flexible client APIs

• External: REST/GraphQL (easy to consume)
• Internal: gRPC (fast, typed)
• Async: NATS/Kafka (decoupling)

My Recommendation

For most Go microservices:

1. Start with gRPC for synchronous service-to-service
2. Add NATS for async events (lightweight, Go-friendly)
3. Use REST only for public-facing APIs

Simple setup? REST everywhere

High performance? gRPC + NATS

Enterprise scale? gRPC + Kafka

Recommended Modern Stack

Hybrid Approach (Most Common):

┌─────────────┐
│ Client      │
└──────┬──────┘
       │ REST/GraphQL
┌──────▼──────────┐
│ API Gateway     │
└──────┬──────────┘
       │ gRPC
   ┌───┴──┬───────┬───────┐
   │      │       │       │
┌──▼──┐ ┌─▼──┐ ┌──▼──┐ ┌──▼──┐
│Auth │ │User│ │Order│ │Pay │
└─────┘ └────┘ └─────┘ └─────┘
   │      │       │       │
   └──────┴───┬───┴───────┘
              │ NATS/Kafka
          ┌───▼────┐
          │ Events │
          └────────┘