Part 7: Only 2 Out of 30 Devs Could Answer This Simple Microservices Question in Node.js

Interview Question: How Would You Set Up Communication Between Two Node.js Services?

Image from Google

This was the question I asked to multiple developers in interviews.

“You’ve split your Node.js app into two services
— one for authentication
— one for user profiles.
How will they talk to each other?”

Only 2 developers gave a clear, structured answer.
The rest? Either went silent or answered with “I’d just use Axios.”

Let’s unpack this — clearly and practically.

Confusing

First: Why Split Your App into Services?

Let’s say your app is growing. Your login logic, profile pages, payments — everything lives in a single repo. Updating one part means testing the whole thing.

That’s where microservices help.
They allow you to:

  • Separate responsibilities
  • Deploy features independently
  • Scale parts of the app differently

But here’s the catch — services need a way to talk.

Why????

So, How Do Microservices Communicate in Node.js?

There are two common ways:

🧩 1. HTTP Communication (Easy & Direct)

You expose APIs in each service and use tools like fetch() or Axios to call them.

// Auth Service
app.post('/login', (req, res) => {
 // Authenticate
});

// User Service calling Auth
const axios = require('axios');
await axios.post('http://auth-service/login', { email, password });
✅ Simple setup, easy to debug.
❌ But tightly coupled and fragile if services go down.

2. Message Queues (Recommended for Decoupling)

Use tools like:

  • Redis Queue (Bull/BullMQ)
  • RabbitMQ
  • Amazon SQS — Read more here

Your services send events into a queue and other services listen for them.

Example:
Login triggers an event → User service listens → Sends welcome email.

✅ Reliable and async
❌ Slightly more setup, but much more scalable and reliable
Queues

What You Should Say in an Interview

Here’s a solid beginner-friendly answer:

“I’d expose REST endpoints in both services. For loose coupling, I’d also consider using a message queue like Redis or RabbitMQ for event-driven tasks like emails or notifications.”

That’s it.
You’ve just shown awareness of microservice communication patterns. 💥

I am smart

🧪 Quiz Time

Q: Which of these is the most reliable way to connect Node.js microservices?

A. Use require() to import one service into another

B. Send API calls using Axios only

C. Use a message broker like RabbitMQ or Redis queues

D. Store all user data in a JSON file

✅ Let me know your answer in the comments.

Quiz Time

Real-World Example

Netflix uses event-driven communication to trigger subtitles, translations, and recommendations — all in separate services. They don’t sync every call with every service in real-time.

Even your startup app can benefit from this structure.

Netflix

Final Thoughts

The goal isn’t to make things more complex — it’s to make them more modular and resilient.

And next time someone asks you how services talk — you’ll know exactly what to say.

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