diff --git a/backend/migrations/0010_users.sql b/backend/migrations/0010_users.sql
index 75c286c..7cb23fd 100644
--- a/backend/migrations/0010_users.sql
+++ b/backend/migrations/0010_users.sql
@@ -1,5 +1,9 @@
 CREATE TABLE IF NOT EXISTS users (
   id INTEGER PRIMARY KEY,
+  userId TEXT DEFAULT (HEX(RANDOMBLOB(4))) NOT NULL UNIQUE,
   username VARCHAR(255) NOT NULL UNIQUE,
   password VARCHAR(255) NOT NULL
-);
\ No newline at end of file
+);
+
+CREATE INDEX IF NOT EXISTS users_username_index ON users (username);
+CREATE INDEX IF NOT EXISTS users_userId_index ON users (userId);
\ No newline at end of file
diff --git a/backend/migrations/0020_projects.sql b/backend/migrations/0020_projects.sql
index 293aea5..8592e75 100644
--- a/backend/migrations/0020_projects.sql
+++ b/backend/migrations/0020_projects.sql
@@ -1,7 +1,11 @@
 CREATE TABLE IF NOT EXISTS projects (
   id INTEGER PRIMARY KEY,
-  name VARCHAR(255) NOT NULL,
+  projectId TEXT DEFAULT (HEX(RANDOMBLOB(4))) NOT NULL UNIQUE,
+  name VARCHAR(255) NOT NULL UNIQUE,
   description TEXT NOT NULL,
   user_id INTEGER NOT NULL,
   FOREIGN KEY (user_id) REFERENCES users (id)
-);
\ No newline at end of file
+);
+
+CREATE INDEX IF NOT EXISTS projects_projectId_index ON projects (projectId);
+CREATE INDEX IF NOT EXISTS projects_user_id_index ON projects (user_id);
\ No newline at end of file
diff --git a/backend/migrations/0030_time_reports.sql b/backend/migrations/0030_time_reports.sql
index b860a35..e8f3ec1 100644
--- a/backend/migrations/0030_time_reports.sql
+++ b/backend/migrations/0030_time_reports.sql
@@ -1,9 +1,10 @@
 CREATE TABLE IF NOT EXISTS time_reports (
   id INTEGER PRIMARY KEY,
+  reportId TEXT DEFAULT (HEX(RANDOMBLOB(6))) NOT NULL UNIQUE,
   project_id INTEGER NOT NULL,
   start DATETIME NOT NULL,
   end DATETIME NOT NULL,
-  FOREIGN KEY (project_id) REFERENCES projects (id)
+  FOREIGN KEY (project_id) REFERENCES projects (id) ON DELETE CASCADE
 );
 
 CREATE TRIGGER IF NOT EXISTS time_reports_start_before_end
diff --git a/backend/migrations/0040_time_report_collections.sql b/backend/migrations/0040_time_report_collections.sql
index 7dbe6bd..be406ff 100644
--- a/backend/migrations/0040_time_report_collections.sql
+++ b/backend/migrations/0040_time_report_collections.sql
@@ -1,7 +1,9 @@
 CREATE TABLE IF NOT EXISTS report_collection (
   id INTEGER PRIMARY KEY,
+  owner_id INTEGER NOT NULL,
   project_id INTEGER NOT NULL,
   date DATE NOT NULL,
   signed_by INTEGER, -- NULL if not signed
+  FOREIGN KEY (owner_id) REFERENCES users (id)
   FOREIGN KEY (signed_by) REFERENCES users (id)
 );
\ No newline at end of file
diff --git a/backend/migrations/0050_user_roles.sql b/backend/migrations/0050_user_roles.sql
index 054593b..32e03dc 100644
--- a/backend/migrations/0050_user_roles.sql
+++ b/backend/migrations/0050_user_roles.sql
@@ -1,7 +1,7 @@
 CREATE TABLE IF NOT EXISTS user_roles (
   user_id INTEGER NOT NULL,
   project_id INTEGER NOT NULL,
-  role STRING NOT NULL,
+  role STRING NOT NULL, -- 'admin' or 'member'
   FOREIGN KEY (user_id) REFERENCES users (id)
   FOREIGN KEY (project_id) REFERENCES projects (id)
 );
\ No newline at end of file