diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 8c8a4c0..95825c6 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -9,6 +9,7 @@
           <set>
             <option value="$PROJECT_DIR$" />
             <option value="$PROJECT_DIR$/core-api" />
+            <option value="$PROJECT_DIR$/core-impl" />
           </set>
         </option>
       </GradleProjectSettings>
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e3648b4
--- /dev/null
+++ b/README.md
@@ -0,0 +1,24 @@
+environment
+-----------
+
+  ```shell
+  docker network create scrow 2>/dev/null || true
+  docker run -d --network scrow -it --rm --name mongo -p 27017:27017 mongo
+  docker run -d --network scrow -e ME_CONFIG_MONGODB_SERVER=mongo -e ME_CONFIG_MONGODB_AUTH_PASSWORD='' -e ME_CONFIG_MONGODB_AUTH_USERNAME='' --name mongo-express -p 8081:8081 mongo-express
+  ```
+
+modules
+-------
+
+* APIs
+  ----
+
+* core-api contains api for all java development
+* core-bukkit-api contains api for bukkit development
+  * depends on core-api
+
+* implementations
+  ---------------
+  the `-impl` suffix indicates that this module implements the API with the same prefix.
+  So `core-impl` implements `core-api`.
+  * core-bukkit-impl is a spigot plugin. It shades core-impl.
\ No newline at end of file
diff --git a/build.gradle.kts b/build.gradle.kts
index b97a06a..4b2a8a6 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,6 +1,6 @@
 plugins {
     id("java")
-    id("java-library")
+    id("io.freefair.lombok") version "9.2.0" apply false
 }
 
 group = "de.kentoj.scrow"
@@ -10,22 +10,27 @@ repositories {
     mavenCentral()
 }
 
-dependencies {
-    testImplementation(platform("org.junit:junit-bom:5.10.0"))
-    testImplementation("org.junit.jupiter:junit-jupiter")
-    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+subprojects {
+    apply(plugin = "java")
+    apply(plugin = "io.freefair.lombok")
 
-    // https://mvnrepository.com/artifact/org.jetbrains/annotations
-    api("org.jetbrains:annotations:26.0.2-1")
+    repositories {
+        mavenCentral()
+    }
 
-    // https://projectreactor.io/docs/core/release/reference/gettingStarted.html
-    api(platform("io.projectreactor:reactor-bom:2025.0.3"))
-    api("io.projectreactor:reactor-core")
+    dependencies {
+        // https://mvnrepository.com/artifact/org.jetbrains/annotations
+        implementation("org.jetbrains:annotations:26.0.2-1")
 
-    // https://mvnrepository.com/artifact/com.google.guava/guava
-    api("com.google.guava:guava:33.5.0-jre")
-}
+        // https://projectreactor.io/docs/core/release/reference/gettingStarted.html
+        implementation(platform("io.projectreactor:reactor-bom:2025.0.3"))
+        implementation("io.projectreactor:reactor-core")
 
-tasks.test {
-    useJUnitPlatform()
+        // https://mvnrepository.com/artifact/com.google.guava/guava
+        implementation("com.google.guava:guava:33.5.0-jre")
+
+        // https://www.mongodb.com/docs/drivers/java/sync/current/get-started/
+        implementation(platform("org.mongodb:mongodb-driver-bom:5.6.3"))
+        implementation("org.mongodb:mongodb-driver-sync")
+    }
 }
\ No newline at end of file
diff --git a/core-impl/src/main/java/de/kentoj/scrow/economy/EconomyServiceImpl.java b/core-impl/src/main/java/de/kentoj/scrow/economy/EconomyServiceImpl.java
new file mode 100644
index 0000000..a8a036a
--- /dev/null
+++ b/core-impl/src/main/java/de/kentoj/scrow/economy/EconomyServiceImpl.java
@@ -0,0 +1,4 @@
+package de.kentoj.scrow.economy;
+
+public class EconomyServiceImpl {
+}
diff --git a/core-impl/src/main/java/de/kentoj/scrow/economy/Main.java b/core-impl/src/main/java/de/kentoj/scrow/economy/Main.java
new file mode 100644
index 0000000..2fa6244
--- /dev/null
+++ b/core-impl/src/main/java/de/kentoj/scrow/economy/Main.java
@@ -0,0 +1,8 @@
+package de.kentoj.scrow.economy;
+
+public class Main {
+    public static void main(String[] args) {
+        var a = new MongoDbHelper();
+        a.close();
+    }
+}
diff --git a/core-impl/src/main/java/de/kentoj/scrow/economy/MongoDbHelper.java b/core-impl/src/main/java/de/kentoj/scrow/economy/MongoDbHelper.java
new file mode 100644
index 0000000..409d889
--- /dev/null
+++ b/core-impl/src/main/java/de/kentoj/scrow/economy/MongoDbHelper.java
@@ -0,0 +1,25 @@
+package de.kentoj.scrow.economy;
+
+import com.mongodb.client.MongoClient;
+import com.mongodb.client.MongoClients;
+import com.mongodb.client.MongoDatabase;
+import lombok.Getter;
+
+import java.io.Closeable;
+
+public class MongoDbHelper implements Closeable {
+
+    private final MongoClient con;
+    @Getter
+    private final MongoDatabase database;
+
+    public MongoDbHelper() {
+        con = MongoClients.create("mongodb://:@localhost:27017/db?ssl=false");
+        database = con.getDatabase("scrow");
+    }
+
+    @Override
+    public void close() {
+        con.close();
+    }
+}
diff --git a/settings.gradle.kts b/settings.gradle.kts
index 7f32556..cb02752 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -1,2 +1,3 @@
 rootProject.name = "core"
-include("core-api")
\ No newline at end of file
+include("core-api")
+include("core-impl")
\ No newline at end of file