Kotlin and PostgreSQL: Building a Backend Faster Than You Thought

Kotlin and PostgreSQL: An Unexpected Duo for Your Backend

When it comes to modern backend development, Kotlin and PostgreSQL are increasingly found in the same sentence. And this is no coincidence. Kotlin brings conciseness and functional features to the JVM world, while PostgreSQL remains the benchmark of reliability and flexibility among relational databases. In this guide, we'll explore how to make these two technologies work together, write real code, and review best practices.

Whether you're already familiar with Kotlin for backend or just starting out — this article will give you a clear action plan. Let's go!

Why Kotlin + PostgreSQL is Awesome?

Kotlin is a language that makes you fall in love from the first lines. It's compatible with Java but eliminates tons of boilerplate. And PostgreSQL is not just "another database." It's a powerful tool with support for JSON, full-text search, window functions, and extensions like PostGIS.

Together they provide:

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• Type-level null safety — Kotlin protects you from NPE when working with query results.
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• Asynchrony out of the box — Kotlin coroutines are perfect for working with connection pools.
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• DSL for SQL — libraries like Exposed allow you to write queries as part of the language.
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• Performance — JVM + optimized JDBC driver provide excellent speed.
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Environment Setup: What You Need to Install

Before writing code, make sure you have:

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• JDK 17+ installed
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• IntelliJ IDEA (Community Edition will do)
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• PostgreSQL 14+ (can be via Docker: docker run --name pg -e POSTGRES_PASSWORD=pass -p 5432:5432 -d postgres)
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• Basic understanding of SQL
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Create a new Gradle project in IntelliJ. In build.gradle.kts, add the dependencies:

dependencies {\n    implementation("org.jetbrains.exposed:exposed-core:0.44.1")\n    implementation("org.jetbrains.exposed:exposed-dao:0.44.1")\n    implementation("org.jetbrains.exposed:exposed-jdbc:0.44.1")\n    implementation("org.postgresql:postgresql:42.7.1")\n    implementation("com.zaxxer:HikariCP:5.1.0")\n    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")\n}

Connecting to PostgreSQL via HikariCP

To work with PostgreSQL in Kotlin, we need a connection pool. HikariCP is the de facto standard. It's fast, lightweight, and configurable in a few lines.

Let's create a DatabaseFactory class:

import com.zaxxer.hikari.HikariConfig\nimport com.zaxxer.hikari.HikariDataSource\nimport org.jetbrains.exposed.sql.Database\n\nobject DatabaseFactory {\n    fun init() {\n        val config = HikariConfig().apply {\n            jdbcUrl = "jdbc:postgresql://localhost:5432/yourdb"\n            driverClassName = "org.postgresql.Driver"\n            username = "postgres"\n            password = "pass"\n            maximumPoolSize = 10\n            isAutoCommit = false\n            transactionIsolation = "TRANSACTION_REPEATABLE_READ"\n        }\n\n        val dataSource = HikariDataSource(config)\n        Database.connect(dataSource)\n    }\n}

Note: isAutoCommit = false gives us control over transactions. This is important for data consistency.

Creating Tables with Exposed ORM

Exposed is a lightweight ORM for Kotlin that doesn't impose its own rules. You can work with both DSL and DAO objects.

Let's define a user model:

import org.jetbrains.exposed.sql.Table\n\nobject Users : Table("users") {\n    val id = integer("id").autoIncrement()\n    val name = varchar("name", 100)\n    val email = varchar("email", 255).uniqueIndex()\n    val