From Java to Kotlin: migrating microservices at Grindr

1. Avoid monolithic architecture

• Grindr’s journey from a Java monolith to microservices using Kotlin.
• Start with a small service and gradually split it out.

2. Less typing with Kotlin

• Kotlin has nice wrappers for things that require less typing.
• System.out.println has a wrapper for example.

3. Switching from Java to Kotlin

• Learning to write Kotlin code was a challenge.
• It’s not always easy to take a temperature from the team.

4. Benefits of Kotlin

• Lot of nice features, like functional error handling.
• Immutability is easier with Kotlin.

5. Improper handling of exceptions in Java

• Grindr had to deal with null pointer exceptions and brittle exception management.

6. Less off-the-shelf libraries

• Writing custom libraries and utilities is more common with Kotlin.
• Sam, a developer on the team, is prolific in creating and sharing Kotlin libraries.

7. Microservices increased complexity

• With 200 services, added complexity, but benefits outweigh the pain.
• Concurrency is core to the language, which is good for microservices.

8. Migrating to Kotlin

• Learned to write Kotlin code, but still struggled sometimes.
• Point at which Grindr started migrating to Kotlin was 2020.

9. API call latency reduced

• API call latency between services improved with the new services.
• New services are smaller and faster, reducing overall latency.

10. Kotlin for Android development

• Kotlin is the preferred language for Android development, and Grindr’s Android team uses it.

11. AWS support for Kotlin

• Grindr’s services run in Docker containers, with no issues in terms of AWS support for Kotlin.

12. Immutability and concurrency

• Immutability is a benefit of Kotlin, making it easier to write concurrent code.