diff --git a/src/main/g8/backend/.scalafmt.conf b/src/main/g8/backend/.scalafmt.conf
new file mode 100644
index 0000000..755b21e
--- /dev/null
+++ b/src/main/g8/backend/.scalafmt.conf
@@ -0,0 +1,2 @@
+version = "3.7.3"
+runner.dialect = scala213
\ No newline at end of file
diff --git a/src/main/g8/backend/README.md b/src/main/g8/backend/README.md
new file mode 100644
index 0000000..ecd0bf0
--- /dev/null
+++ b/src/main/g8/backend/README.md
@@ -0,0 +1,105 @@
+# Scalajs backend app
+
+## Routes
+
+### GET /todos
+
+Returns a list of todos tasks
+
+_Response example:_
+
+```json
+[
+  {
+    "id": 1,
+    "title": "Todo 1",
+    "completed": false
+  },
+  {
+    "id": 2,
+    "title": "Todo 2",
+    "completed": false
+  },
+  {
+    "id": 3,
+    "title": "Todo 3",
+    "completed": false
+  }
+]
+```
+
+### GET /todos/:id
+
+Returns a todo task
+
+_Response example:_
+
+```json
+{
+  "id": 1,
+  "title": "Todo 1",
+  "completed": false
+}
+```
+
+### POST /todos?title=string
+
+Creates a todo task
+
+_Response example:_
+
+```json
+{
+  "id": 1,
+  "title": "Todo 1",
+  "completed": false
+}
+```
+
+### PUT /todos/:id?title=string
+
+Updates a todo task by changing the title field
+
+_Response example:_
+
+```json
+{
+  "id": 1,
+  "title": "Todo 1",
+  "completed": false
+}
+```
+
+### POST /todos/:id/completed
+
+Updates a todo task by changing the completed status
+
+_Response example:_
+
+```json
+{
+  "id": 1,
+  "title": "Todo 1",
+  "completed": true
+}
+```
+
+### DELETE /todos/:id
+
+Deletes a todo task
+
+_Response example:_
+
+```text
+Task 1 has been deleted
+```
+
+### DELETE /todos/completed
+
+Deletes all completed todo tasks
+
+_Response example:_
+
+```text
+All completed tasks have been deleted
+```
diff --git a/src/main/g8/backend/build.sbt b/src/main/g8/backend/build.sbt
index da76952..79c9122 100644
--- a/src/main/g8/backend/build.sbt
+++ b/src/main/g8/backend/build.sbt
@@ -1,9 +1,18 @@
 // give the user a nice default project!
 ThisBuild / organization := "com.do"
-ThisBuild / scalaVersion := "2.12.8"
+ThisBuild / scalaVersion := "2.13.10"
 
-lazy val root = (project in file(".")).
-  settings(
-    name := "Fullstack Scaffhold",
-    mainClass := Some("com.do.Main")
+lazy val root = (project in file(".")).settings(
+  name := "Fullstack Scaffhold",
+  mainClass := Some("com.do.Main"),
+  libraryDependencies ++= Seq(
+    "dev.zio" %% "zio" % "2.0.14",
+    "dev.zio" %% "zio-http" % "3.0.0-RC1",
+    "dev.zio" %% "zio-sql" % "0.1.2",
+    "dev.zio" %% "zio-sql-postgres" % "0.1.2",
+    "dev.zio" %% "zio-streams" % "1.0.12",
+    "dev.zio" %% "zio-interop-cats" % "3.1.1.0",
+    "org.mongodb.scala" %% "mongo-scala-driver" % "4.9.1",
+    "org.mongodb.scala" %% "mongo-scala-bson" % "4.9.1"
   )
+)
diff --git a/src/main/g8/backend/data.json b/src/main/g8/backend/data.json
new file mode 100644
index 0000000..c0c2d3e
--- /dev/null
+++ b/src/main/g8/backend/data.json
@@ -0,0 +1,12 @@
+[
+  {
+    "id": 1,
+    "title": "Faire du sale",
+    "completed": false
+  },
+  {
+    "id": 2,
+    "title": "Manger du poulet",
+    "completed": false
+  }
+]
diff --git a/src/main/g8/backend/docker-compose.yaml b/src/main/g8/backend/docker-compose.yaml
new file mode 100644
index 0000000..586b4e0
--- /dev/null
+++ b/src/main/g8/backend/docker-compose.yaml
@@ -0,0 +1,17 @@
+# Use root/example as user/password credentials
+version: '3.1'
+
+services:
+  mongo:
+    image: mongo
+    ports:
+      - 27018:27017
+    environment:
+      - MONGO_INITDB_ROOT_USERNAME=root
+      - MONGO_INITDB_ROOT_PASSWORD=root
+      - MONGO_INITDB_DATABASE=todo_app
+    volumes:
+      - mongodb_data_todo_app:/data/db
+
+volumes:
+  mongodb_data_todo_app:
diff --git a/src/main/g8/backend/project/metals.sbt b/src/main/g8/backend/project/metals.sbt
new file mode 100644
index 0000000..05fd2b3
--- /dev/null
+++ b/src/main/g8/backend/project/metals.sbt
@@ -0,0 +1,6 @@
+// DO NOT EDIT! This file is auto-generated.
+
+// This file enables sbt-bloop to create bloop config files.
+
+addSbtPlugin("ch.epfl.scala" % "sbt-bloop" % "1.5.6")
+
diff --git a/src/main/g8/backend/project/project/metals.sbt b/src/main/g8/backend/project/project/metals.sbt
new file mode 100644
index 0000000..05fd2b3
--- /dev/null
+++ b/src/main/g8/backend/project/project/metals.sbt
@@ -0,0 +1,6 @@
+// DO NOT EDIT! This file is auto-generated.
+
+// This file enables sbt-bloop to create bloop config files.
+
+addSbtPlugin("ch.epfl.scala" % "sbt-bloop" % "1.5.6")
+
diff --git a/src/main/g8/backend/src/main/scala/DB.scala b/src/main/g8/backend/src/main/scala/DB.scala
new file mode 100644
index 0000000..166bf47
--- /dev/null
+++ b/src/main/g8/backend/src/main/scala/DB.scala
@@ -0,0 +1,30 @@
+package todo
+
+import org.bson.codecs.configuration.CodecRegistry
+import org.bson.codecs.configuration.CodecRegistries.{
+  fromProviders,
+  fromRegistries
+}
+import org.mongodb.scala.{MongoClient, MongoCollection}
+import org.mongodb.scala.MongoClient.DEFAULT_CODEC_REGISTRY
+import org.mongodb.scala.bson.codecs.Macros._
+
+object DB {
+  private val databaseURL: String =
+    Option(System.getenv("MONGO_URL"))
+      .getOrElse("mongodb://root:root@localhost:27018")
+
+  private val customCodecs: CodecRegistry =
+    fromProviders(classOf[Todo])
+
+  private val codecRegistry: CodecRegistry =
+    fromRegistries(customCodecs, DEFAULT_CODEC_REGISTRY)
+
+  private val database =
+    MongoClient(databaseURL)
+      .getDatabase("todoapp")
+      .withCodecRegistry(codecRegistry)
+
+  val todosCollection: MongoCollection[Todo] =
+    database.getCollection[Todo]("todos")
+}
diff --git a/src/main/g8/backend/src/main/scala/Main.scala b/src/main/g8/backend/src/main/scala/Main.scala
index 54ccbec..1a60181 100644
--- a/src/main/g8/backend/src/main/scala/Main.scala
+++ b/src/main/g8/backend/src/main/scala/Main.scala
@@ -1,5 +1,20 @@
-object Main {
-  def main(args: Array[String]): Unit = {
-    println("Hello, world")
-  }
-}
\ No newline at end of file
+package todo
+
+import zio._
+import zio.http._
+
+object TodoApp extends ZIOAppDefault {
+  val port: Int =
+    sys.env
+      .get("PORT")
+      .filter(_.nonEmpty)
+      .map(_.toInt)
+      .getOrElse(8080)
+
+  private val config = Server.Config.default.port(port)
+  private val configLayer = ZLayer.succeed(config)
+
+  printf("Server listening on http://localhost:%d\n", port)
+  override val run =
+    Server.serve(TodoController.routes).provide(configLayer, Server.live)
+}
diff --git a/src/main/g8/backend/src/main/scala/Todo.scala b/src/main/g8/backend/src/main/scala/Todo.scala
new file mode 100644
index 0000000..e42ebd6
--- /dev/null
+++ b/src/main/g8/backend/src/main/scala/Todo.scala
@@ -0,0 +1,14 @@
+package todo
+
+import zio.json._
+
+case class Todo(
+    id: Int,
+    title: String,
+    completed: Boolean
+)
+
+object Todo {
+  implicit val todoEncoder: JsonEncoder[Todo] = DeriveJsonEncoder.gen[Todo]
+  implicit val todoDecoder: JsonDecoder[Todo] = DeriveJsonDecoder.gen[Todo]
+}
diff --git a/src/main/g8/backend/src/main/scala/TodoController.scala b/src/main/g8/backend/src/main/scala/TodoController.scala
new file mode 100644
index 0000000..57cf796
--- /dev/null
+++ b/src/main/g8/backend/src/main/scala/TodoController.scala
@@ -0,0 +1,121 @@
+package todo
+
+import zio._
+import zio.http._
+import zio.json._
+
+object TodoController {
+
+  val BasePath = !! / "todos"
+
+  val routes: Http[Any, Nothing, Request, Response] =
+    Http.collectZIO[Request] {
+      case Method.GET -> BasePath => {
+        TodoService
+          .getTodos()
+          .map(_.toJson)
+          .map(Response.text(_))
+          .orElse(
+            ZIO.succeed(
+              Response.fromHttpError(
+                HttpError.NotFound("No todos found")
+              )
+            )
+          )
+      }
+      case Method.GET -> BasePath / id => {
+        if (id.forall(_.isDigit)) {
+          TodoService
+            .getTodoById(id.toInt)
+            .map(_.toJson)
+            .map(Response.text(_))
+            .orElse(
+              ZIO.succeed(
+                Response.fromHttpError(
+                  HttpError.NotFound(s"Todo with ID $id not found")
+                )
+              )
+            )
+        } else {
+          ZIO.succeed(
+            Response.fromHttpError(HttpError.BadRequest("Invalid ID format"))
+          )
+        }
+      }
+      case req @ Method.POST -> BasePath => {
+        (for {
+          queryParams <- ZIO
+            .fromOption(Option(req.url.queryParams))
+            .orElseFail(HttpError.BadRequest("Missing query parameters"))
+          title <- ZIO
+            .fromOption(queryParams.get("title").collect(_.head))
+            .orElseFail(HttpError.BadRequest("Missing 'title' parameter"))
+          createdTodo <- TodoService.createTodo(title)
+        } yield createdTodo)
+          .fold(
+            error => Response.fromHttpError(HttpError.InternalServerError()),
+            todo => Response.text(todo.toJson)
+          )
+      }
+      case req @ Method.PUT -> BasePath / id => {
+        (for {
+          queryParams <- ZIO
+            .fromOption(Option(req.url.queryParams))
+            .orElseFail(HttpError.BadRequest("Missing query parameters"))
+          title <- ZIO
+            .fromOption(queryParams.get("title").collect(_.head))
+            .orElseFail(HttpError.BadRequest("Missing 'title' parameter"))
+          updatedTodo <- TodoService.updateTodoTitleField(id.toInt, title)
+        } yield updatedTodo)
+          .fold(
+            error => Response.fromHttpError(HttpError.InternalServerError()),
+            todo => Response.text(todo.toJson)
+          )
+      }
+      case Method.POST -> BasePath / id / "completed" => {
+        if (id.forall(_.isDigit)) {
+          TodoService
+            .updateTodoCompletedField(id.toInt)
+            .map(_.toJson)
+            .map(Response.text(_))
+            .orElse(
+              ZIO.succeed(
+                Response.fromHttpError(
+                  HttpError.NotFound(s"Todo with ID $id not found")
+                )
+              )
+            )
+        } else {
+          ZIO.succeed(Response.fromHttpError(HttpError.BadRequest()))
+        }
+      }
+      case Method.DELETE -> BasePath / "completed" => {
+        TodoService
+          .deleteCompletedTodo()
+          .map(_ => Response.text("All completed tasks have been deleted"))
+          .orElse(
+            ZIO.succeed(
+              Response.fromHttpError(
+                HttpError.InternalServerError("Error deleting completed tasks")
+              )
+            )
+          )
+      }
+      case Method.DELETE -> BasePath / id => {
+        if (id.forall(_.isDigit)) {
+          TodoService
+            .deleteTodoById(id.toInt)
+            .map(_ => Response.text(s"Task $id has been deleted"))
+            .orElse(
+              ZIO.succeed(
+                Response.fromHttpError(
+                  HttpError.NotFound(s"Todo with ID $id not found")
+                )
+              )
+            )
+        } else {
+          ZIO.succeed(Response.fromHttpError(HttpError.BadRequest()))
+        }
+      }
+    }
+}
diff --git a/src/main/g8/backend/src/main/scala/TodoService.scala b/src/main/g8/backend/src/main/scala/TodoService.scala
new file mode 100644
index 0000000..8f5fbbe
--- /dev/null
+++ b/src/main/g8/backend/src/main/scala/TodoService.scala
@@ -0,0 +1,96 @@
+package todo
+
+import zio.Task
+import zio._
+
+import org.mongodb.scala.model.Filters._
+import org.mongodb.scala.model.Updates._
+
+import org.mongodb.scala.MongoCollection
+
+object TodoService {
+  private val todosCollection: MongoCollection[Todo] = DB.todosCollection
+
+  def getTodos(): Task[Seq[Todo]] =
+    ZIO.fromFuture(_ => todosCollection.find().toFuture())
+
+  def getTodoById(id: Int): Task[Option[Todo]] =
+    ZIO.fromFuture(_ => todosCollection.find(equal("id", id)).headOption())
+
+  def createTodo(title: String): Task[Todo] =
+    for {
+      todos <- getTodos()
+      newId = todos.map(_.id).max + 1
+      newTodo = Todo(newId, title, false)
+      _ <- ZIO
+        .fromFuture(_ => todosCollection.insertOne(newTodo).toFuture())
+        .unit
+    } yield newTodo
+
+  def updateTodoTitleField(todoId: Int, title: String): Task[Todo] =
+    for {
+      taskToChange <- getTodoById(todoId)
+      updatedTodo <- taskToChange match {
+        case Some(todo) =>
+          val updated = todo.copy(title = title)
+          ZIO
+            .fromFuture(_ =>
+              todosCollection
+                .updateOne(equal("id", todoId), set("title", updated.title))
+                .toFuture()
+            )
+            .map(_ => updated)
+        case None =>
+          ZIO.fail(
+            new NoSuchElementException(s"Todo with ID $todoId not found")
+          )
+      }
+    } yield updatedTodo
+
+  def updateTodoCompletedField(todoId: Int): Task[Todo] =
+    for {
+      taskToChange <- getTodoById(todoId)
+      updatedTodo <- taskToChange match {
+        case Some(todo) =>
+          val updated = todo.copy(completed = !todo.completed)
+          ZIO
+            .fromFuture(_ =>
+              todosCollection
+                .updateOne(
+                  equal("id", todoId),
+                  set("completed", updated.completed)
+                )
+                .toFuture()
+            )
+            .map(_ => updated)
+        case None =>
+          ZIO.fail(
+            new NoSuchElementException(s"Todo with ID $todoId not found")
+          )
+      }
+    } yield updatedTodo
+
+  def deleteTodoById(id: Int): Task[Unit] =
+    ZIO
+      .fromFuture(_ => todosCollection.deleteOne(equal("id", id)).toFuture())
+      .flatMap { result =>
+        if (result.wasAcknowledged() && result.getDeletedCount == 0) {
+          ZIO.fail(new Exception("Todo not found"))
+        } else {
+          ZIO.unit
+        }
+      }
+
+  def deleteCompletedTodo(): Task[Unit] =
+    ZIO
+      .fromFuture(_ =>
+        todosCollection.deleteMany(equal("completed", true)).toFuture()
+      )
+      .flatMap { result =>
+        if (result.wasAcknowledged() && result.getDeletedCount == 0) {
+          ZIO.fail(new Exception("No todo deleted"))
+        } else {
+          ZIO.unit
+        }
+      }
+}