diff --git a/crates/back/src/cli.rs b/crates/back/src/cli.rs
index a32b80437f09a133dbf6c0efca70ee8562ca300e..8c86371cddc578fed93fb9306c28d49a461e6b84 100644
--- a/crates/back/src/cli.rs
+++ b/crates/back/src/cli.rs
@@ -59,7 +59,7 @@ impl FromStr for DatabaseConfig {
             return Ok(Self::None);
         }
 
-        let (left, right) = s.split_once("=").ok_or_else(|| "missing '='".to_owned())?;
+        let (left, right) = s.split_once('=').ok_or_else(|| "missing '='".to_owned())?;
 
         match left {
             #[cfg(feature = "postgres_db")]
diff --git a/crates/back/src/db/any.rs b/crates/back/src/db/any.rs
index 3012bd13c345547c7ce81aa13ad42750237e0782..e328b01c8176baa9505603012a16364d0c07b492 100644
--- a/crates/back/src/db/any.rs
+++ b/crates/back/src/db/any.rs
@@ -4,7 +4,7 @@ use argon2::{
     password_hash::{rand_core::OsRng, SaltString},
     Argon2, PasswordHash, PasswordHasher,
 };
-use std::{future::Future, ops::Deref, pin::Pin};
+use std::{future::Future, pin::Pin};
 use uuid::Uuid;
 
 //
@@ -37,7 +37,7 @@ pub(super) type GetUserFut<'a> = DbFut<'a, Result<Option<DbUser>, DbError>>;
 pub(super) trait DatabaseImpl {
     // TODO: https://github.com/rust-lang/rust/issues/91611
 
-    fn get_courses<'a>(&'a self) -> GetCoursesFut<'a>;
+    fn get_courses(&self) -> GetCoursesFut;
 
     fn create_user<'a>(
         &'a self,
@@ -121,7 +121,7 @@ impl AnyDatabase {
 } */
 
 impl DatabaseImpl for AnyDatabase {
-    fn get_courses<'a>(&'a self) -> GetCoursesFut<'a> {
+    fn get_courses(&self) -> GetCoursesFut {
         match self {
             #[cfg(feature = "postgres_db")]
             AnyDatabase::Postgres(v) => v.get_courses(),
@@ -158,7 +158,7 @@ impl DatabaseImpl for AnyDatabase {
 }
 
 impl DatabaseImpl for () {
-    fn get_courses<'a>(&'a self) -> GetCoursesFut<'a> {
+    fn get_courses(&self) -> GetCoursesFut {
         Box::pin(async { Err(DbError::DatabaseNotConnected) })
     }
 
diff --git a/crates/back/src/db/postgres.rs b/crates/back/src/db/postgres.rs
index 105f0c711b4dec156f70fd03e89065c4467fe74c..393c1bcf6bca451d819f6ca6abac62bc14d88721 100644
--- a/crates/back/src/db/postgres.rs
+++ b/crates/back/src/db/postgres.rs
@@ -1,6 +1,6 @@
 use super::{
     any::{CreateUserFut, DatabaseImpl, GetCoursesFut, GetUserFut},
-    DbCourse, DbCreateUser, DbError, DbUser,
+    DbCreateUser, DbError,
 };
 use argon2::PasswordHash;
 use sqlx::{postgres::PgPoolOptions, PgPool};
@@ -20,7 +20,7 @@ impl Database {
         tracing::debug!("Connecting to pg database");
         let pool = PgPoolOptions::new()
             .max_connections(5)
-            .connect(&db_addr)
+            .connect(db_addr)
             .await?;
 
         // TODO: init db
@@ -30,7 +30,7 @@ impl Database {
 }
 
 impl DatabaseImpl for Database {
-    fn get_courses<'a>(&'a self) -> GetCoursesFut<'a> {
+    fn get_courses(&self) -> GetCoursesFut {
         Box::pin(async move {
             Ok(sqlx::query_as(
                 r#"SELECT id, name, description, points_max
diff --git a/crates/back/src/db/sled.rs b/crates/back/src/db/sled.rs
index 331412547278fc75a15cda76af717b3950ce0650..3d8c208a5e78c5ef3b9edbd22df4658da315dbec 100644
--- a/crates/back/src/db/sled.rs
+++ b/crates/back/src/db/sled.rs
@@ -1,30 +1,25 @@
 use super::{
     any::{CreateUserFut, DatabaseImpl, GetCoursesFut, GetUserFut},
-    DbCourse, DbCreateUser, DbError, DbUser,
+    DbCreateUser, DbError, DbUser,
 };
 use argon2::PasswordHash;
-use sled::{Db, IVec, Tree};
-use std::{
-    future::Future,
-    path::{Path, PathBuf},
-    pin::Pin,
-};
+use sled::{IVec, Tree};
+use std::path::Path;
 use uuid::Uuid;
 
 //
 
 pub struct Database {
-    db: Db,
-
+    /* db: Db, */
     users: Tree,
     courses: Tree,
-    course_admins: Tree,
+    /* course_admins: Tree,
     lessons: Tree,
     exercises: Tree,
 
     course_progress: Tree,
     lesson_progress: Tree,
-    exercise_progress: Tree,
+    exercise_progress: Tree, */
 }
 
 //
@@ -35,31 +30,30 @@ impl Database {
 
         let users = db.open_tree("users")?;
         let courses = db.open_tree("courses")?;
-        let course_admins = db.open_tree("course_admins")?;
+        /* let course_admins = db.open_tree("course_admins")?;
         let lessons = db.open_tree("lessons")?;
         let exercises = db.open_tree("exercises")?;
         let course_progress = db.open_tree("course_progress")?;
         let lesson_progress = db.open_tree("lesson_progress")?;
-        let exercise_progress = db.open_tree("exercise_progress")?;
+        let exercise_progress = db.open_tree("exercise_progress")?; */
 
         Ok(Self {
-            db,
-
+            /* db, */
             users,
             courses,
-            course_admins,
+            /* course_admins,
             lessons,
             exercises,
 
             course_progress,
             lesson_progress,
-            exercise_progress,
+            exercise_progress, */
         })
     }
 }
 
 impl DatabaseImpl for Database {
-    fn get_courses<'a>(&'a self) -> GetCoursesFut<'a> {
+    fn get_courses(&self) -> GetCoursesFut {
         Box::pin(async move {
             self.courses
                 .iter()