Choosing the Communication Protocol

How should your services talk to each other? The choice of protocol affects performance, developer experience, and payload size.

1. REST (The Workhorse)

JSON over HTTP. Pros: Human-readable, works everywhere. Cons: High overhead (text-based), difficult to version securely.

2. gRPC (The High-Performance Choice)

Uses **Protocol Buffers** (Binary) over HTTP/2. Pros: 5-10x faster than REST, tiny payloads, and strong types. Cons: Not browser-friendly (needs a proxy), not human-readable. Perfect for **Internal** service-to-service communication.

3. GraphQL (The Flexible Choice)

Allows the client to ask for exactly the data they need. Pros: No over-fetching, perfect for Mobile apps. Cons: Hard to cache, complex to secure (prevents "N+1" query attacks).

4. Interview Mastery

Q: "Which protocol would you use for internal Microservices communication?"

Architect Answer: "I would use **gRPC**. Because internal calls happen thousands of times per second, the efficiency of a binary protocol and long-lived HTTP/2 connections provides a massive reduction in CPU and Latency compared to parsing large JSON strings over REST. I'd keep **REST/GraphQL** only for the Public-facing API surface."