A Brief (and Slightly Entertaining) History of Microservices

Once upon a time (somewhere around the early 2000s), developers were stuck in monolithic hell—big, bulky applications where a single change could break everything. Think of it like trying to replace a single Lego piece in a giant, glued-together Lego Death Star. Yeah, not fun.

Then came microservices, the superhero of backend architecture. Instead of one gigantic application, microservices broke things down into small, independent services that could be developed, deployed, and scaled separately. Developers rejoiced! Companies rejoiced! And, of course, Kubernetes got way too popular.

Enter Kotlin: The Language That Stole Java’s Lunch Money

Java had been ruling the backend world for years. But it had… baggage. Kotlin showed up in 2011, looked Java in the eye, and said, “Hey, I can do everything you do, but with less boilerplate and more fun.”

By 2017, Google made Kotlin an official language for Android, and soon, backend developers realized it was perfect for microservices, especially with Spring Boot.

So, why Kotlin for microservices?

• Concise – Less boilerplate, more business logic.
• Interoperable – Works seamlessly with Java.
• Null Safety – No more NullPointerException nightmares.
• Coroutines – Makes handling concurrency smooth as butter.

Setting Up a Kotlin Microservice

Enough talk. Let’s code! Here’s how you spin up a basic Kotlin microservice using Spring Boot.

Step 1: Create a Kotlin Spring Boot Project

Use Spring Initializr and select:

• Language: Kotlin
• Dependencies: Spring Web, Spring Boot Actuator

Or just use the good old CLI:

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curl https://start.spring.io/starter.zip -d dependencies=web -d type=gradle-kotlin-project -o demo.zip
unzip demo.zip
cd demo

Step 2: Write a Simple REST Controller

Create a Kotlin file in src/main/kotlin/com/example/demo/HelloController.kt:

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package com.example.demo

import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController

@RestController
@RequestMapping("/api")
class HelloController {
    @GetMapping("/hello")
    fun sayHello(): String {
        return "Hello, Kotlin Microservices!"
    }
}

Boom! You just wrote your first Kotlin microservice endpoint.

Step 3: Run It Like a Boss

Fire up the service:

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./gradlew bootRun

Now hit http://localhost:8080/api/hello and enjoy your hard-earned “Hello, Kotlin Microservices!” response. 🎉

Adding Some Spice: Kotlin Coroutines & Reactive Programming

Want to make your microservice non-blocking? Use coroutines:

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import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController

@RestController
@RequestMapping("/api")
class AsyncController {
    @GetMapping("/async")
    suspend fun getAsyncMessage(): String {
        delay(1000) // Simulates async processing
        return "This was async!"
    }
}

Now, your endpoint won’t block the thread while waiting. Async and fast—just like your favorite instant ramen.

Dockerizing Your Kotlin Microservice

Because no microservice is complete without a Dockerfile:

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FROM openjdk:17
COPY build/libs/demo-0.0.1-SNAPSHOT.jar app.jar
ENTRYPOINT ["java", "-jar", "/app.jar"]

Build and run it:

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docker build -t kotlin-microservice .
docker run -p 8080:8080 kotlin-microservice

Now your service is running in a container, ready to be deployed anywhere!

Scaling It Up with Kubernetes (Because Why Not?)

Define a Kubernetes Deployment:

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apiVersion: apps/v1
kind: Deployment
metadata:
  name: kotlin-microservice
spec:
  replicas: 3
  selector:
    matchLabels:
      app: kotlin-microservice
  template:
    metadata:
      labels:
        app: kotlin-microservice
    spec:
      containers:
        - name: kotlin-microservice
          image: kotlin-microservice:latest
          ports:
            - containerPort: 8080

Now deploy it and watch your Kotlin service scale like a champ.

Key Ideas

References

1. Spring Boot with Kotlin
2. Kotlin Coroutines
3. Dockerizing Spring Boot Apps
4. Kubernetes Deployments