diff --git a/core/database/src/androidMain/kotlin/club/nito/core/database/Database.android.kt b/core/database/src/androidMain/kotlin/club/nito/core/database/Database.android.kt
new file mode 100644
index 00000000..abeb4280
--- /dev/null
+++ b/core/database/src/androidMain/kotlin/club/nito/core/database/Database.android.kt
@@ -0,0 +1,24 @@
+package club.nito.core.database
+
+import android.content.Context
+import androidx.sqlite.db.SupportSQLiteDatabase
+import app.cash.sqldelight.db.SqlDriver
+import app.cash.sqldelight.driver.android.AndroidSqliteDriver
+
+internal actual class DriverFactory(private val context: Context) {
+    actual fun createDriver(): SqlDriver {
+        val schema = Database.Schema
+
+        return AndroidSqliteDriver(
+            schema = schema,
+            context = context,
+            name = DATABASE_NAME,
+            callback = object : AndroidSqliteDriver.Callback(schema) {
+                override fun onConfigure(db: SupportSQLiteDatabase) {
+                    db.enableWriteAheadLogging()
+                    db.setForeignKeyConstraintsEnabled(true)
+                }
+            },
+        )
+    }
+}
diff --git a/core/database/src/androidMain/kotlin/club/nito/core/database/di/DatabaseModule.android.kt b/core/database/src/androidMain/kotlin/club/nito/core/database/di/DatabaseModule.android.kt
new file mode 100644
index 00000000..78c667b3
--- /dev/null
+++ b/core/database/src/androidMain/kotlin/club/nito/core/database/di/DatabaseModule.android.kt
@@ -0,0 +1,8 @@
+package club.nito.core.database.di
+
+import club.nito.core.database.DriverFactory
+import org.koin.core.scope.Scope
+
+internal actual fun Scope.createDriverFactory(): DriverFactory = DriverFactory(
+    context = get(),
+)
diff --git a/core/database/src/commonMain/kotlin/club/nito/core/database/.gitkeep b/core/database/src/commonMain/kotlin/club/nito/core/database/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/core/database/src/commonMain/kotlin/club/nito/core/database/Database.kt b/core/database/src/commonMain/kotlin/club/nito/core/database/Database.kt
new file mode 100644
index 00000000..2cd38947
--- /dev/null
+++ b/core/database/src/commonMain/kotlin/club/nito/core/database/Database.kt
@@ -0,0 +1,23 @@
+package club.nito.core.database
+
+import app.cash.sqldelight.EnumColumnAdapter
+import app.cash.sqldelight.db.SqlDriver
+
+internal expect class DriverFactory {
+    fun createDriver(): SqlDriver
+}
+
+internal const val DATABASE_NAME = "nito.db"
+
+internal fun createDatabase(driverFactory: DriverFactory): Database {
+    val driver = driverFactory.createDriver()
+    val database = Database(
+        driver = driver,
+        participantsAdapter = Participants.Adapter(
+            statusAdapter = EnumColumnAdapter(),
+        ),
+    )
+
+    // Do more work with the database (see below).
+    return database
+}
diff --git a/core/database/src/commonMain/kotlin/club/nito/core/database/adapter/ParticipantStatus.kt b/core/database/src/commonMain/kotlin/club/nito/core/database/adapter/ParticipantStatus.kt
new file mode 100644
index 00000000..c7603e72
--- /dev/null
+++ b/core/database/src/commonMain/kotlin/club/nito/core/database/adapter/ParticipantStatus.kt
@@ -0,0 +1,10 @@
+package club.nito.core.database.adapter
+
+import app.cash.sqldelight.ColumnAdapter
+import club.nito.core.model.participant.ParticipantStatus
+
+internal data object ParticipantStatusAdapter : ColumnAdapter<ParticipantStatus, String> {
+    override fun decode(databaseValue: String): ParticipantStatus = ParticipantStatus.valueOf(databaseValue)
+
+    override fun encode(value: ParticipantStatus): String = value.name
+}
diff --git a/core/database/src/commonMain/kotlin/club/nito/core/database/di/DatabaseModule.kt b/core/database/src/commonMain/kotlin/club/nito/core/database/di/DatabaseModule.kt
new file mode 100644
index 00000000..d0f557b7
--- /dev/null
+++ b/core/database/src/commonMain/kotlin/club/nito/core/database/di/DatabaseModule.kt
@@ -0,0 +1,17 @@
+package club.nito.core.database.di
+
+import club.nito.core.database.DriverFactory
+import club.nito.core.database.createDatabase
+import org.koin.core.module.Module
+import org.koin.core.scope.Scope
+import org.koin.dsl.module
+
+public val databaseModule: Module = module {
+    single {
+        createDatabase(
+            driverFactory = createDriverFactory(),
+        )
+    }
+}
+
+internal expect fun Scope.createDriverFactory(): DriverFactory
diff --git a/core/database/src/commonMain/sqldelight/club/nito/core/database/Participants.sq b/core/database/src/commonMain/sqldelight/club/nito/core/database/Participants.sq
new file mode 100644
index 00000000..80eb56bd
--- /dev/null
+++ b/core/database/src/commonMain/sqldelight/club/nito/core/database/Participants.sq
@@ -0,0 +1,37 @@
+import club.nito.core.model.participant.ParticipantStatus;
+
+CREATE TABLE `participants` (
+  `schedule_id` TEXT NOT NULL,
+  `user_id` TEXT NOT NULL,
+  `status` TEXT AS ParticipantStatus NOT NULL
+);
+
+CREATE UNIQUE INDEX `participants_pkey` ON `participants` (`schedule_id`, `user_id`);
+
+participantsByScheduleId:
+SELECT *
+FROM participants
+WHERE schedule_id = ?;
+
+participantsByUserId:
+SELECT *
+FROM participants
+WHERE user_id = ?;
+
+upsert {
+  UPDATE participants SET
+    `schedule_id` = :schedule_id,
+    `user_id` = :user_id,
+    `status` = :status
+  WHERE schedule_id = :schedule_id AND user_id = :user_id;
+
+  INSERT OR IGNORE INTO participants (
+    `schedule_id`,
+    `user_id`,
+    `status`
+  ) VALUES (
+    :schedule_id,
+    :user_id,
+    :status
+  );
+}
diff --git a/core/database/src/androidMain/kotlin/club/nito/core/database/.gitkeep b/core/database/src/commonMain/sqldelight/migrations/1.sqm
similarity index 100%
rename from core/database/src/androidMain/kotlin/club/nito/core/database/.gitkeep
rename to core/database/src/commonMain/sqldelight/migrations/1.sqm
diff --git a/core/database/src/iosMain/kotlin/club/nito/core/database/.gitkeep b/core/database/src/iosMain/kotlin/club/nito/core/database/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/core/database/src/iosMain/kotlin/club/nito/core/database/Database.ios.kt b/core/database/src/iosMain/kotlin/club/nito/core/database/Database.ios.kt
new file mode 100644
index 00000000..b2ac0750
--- /dev/null
+++ b/core/database/src/iosMain/kotlin/club/nito/core/database/Database.ios.kt
@@ -0,0 +1,11 @@
+package club.nito.core.database
+
+import app.cash.sqldelight.db.SqlDriver
+import app.cash.sqldelight.driver.native.NativeSqliteDriver
+
+internal actual class DriverFactory {
+    actual fun createDriver(): SqlDriver = NativeSqliteDriver(
+        schema = Database.Schema,
+        name = DATABASE_NAME,
+    )
+}
diff --git a/core/database/src/iosMain/kotlin/club/nito/core/database/di/DatabaseModule.ios.kt b/core/database/src/iosMain/kotlin/club/nito/core/database/di/DatabaseModule.ios.kt
new file mode 100644
index 00000000..10d00dd6
--- /dev/null
+++ b/core/database/src/iosMain/kotlin/club/nito/core/database/di/DatabaseModule.ios.kt
@@ -0,0 +1,6 @@
+package club.nito.core.database.di
+
+import club.nito.core.database.DriverFactory
+import org.koin.core.scope.Scope
+
+internal actual fun Scope.createDriverFactory(): DriverFactory = DriverFactory()
diff --git a/core/database/src/jsMain/kotlin/club/nito/core/database/Database.js.kt b/core/database/src/jsMain/kotlin/club/nito/core/database/Database.js.kt
new file mode 100644
index 00000000..8d9506ba
--- /dev/null
+++ b/core/database/src/jsMain/kotlin/club/nito/core/database/Database.js.kt
@@ -0,0 +1,15 @@
+package club.nito.core.database
+
+import app.cash.sqldelight.db.SqlDriver
+import app.cash.sqldelight.driver.worker.WebWorkerDriver
+import org.w3c.dom.Worker
+
+internal actual class DriverFactory {
+    actual fun createDriver(): SqlDriver {
+        return WebWorkerDriver(
+            Worker(
+                js("""new URL("@cashapp/sqldelight-sqljs-worker/sqljs.worker.js", import.meta.url)""")
+            )
+        ).also { Database.Schema.create(it) }
+    }
+}
diff --git a/core/database/src/jsMain/kotlin/club/nito/core/database/di/DatabaseModule.js.kt b/core/database/src/jsMain/kotlin/club/nito/core/database/di/DatabaseModule.js.kt
new file mode 100644
index 00000000..10d00dd6
--- /dev/null
+++ b/core/database/src/jsMain/kotlin/club/nito/core/database/di/DatabaseModule.js.kt
@@ -0,0 +1,6 @@
+package club.nito.core.database.di
+
+import club.nito.core.database.DriverFactory
+import org.koin.core.scope.Scope
+
+internal actual fun Scope.createDriverFactory(): DriverFactory = DriverFactory()