diff --git a/api/modules/session/controllers/SessionController.php b/api/modules/session/controllers/SessionController.php
index 6e88b11..4e1fc34 100644
--- a/api/modules/session/controllers/SessionController.php
+++ b/api/modules/session/controllers/SessionController.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace api\modules\session\controllers;
 
 use api\controllers\Controller;
@@ -31,18 +33,23 @@ class SessionController extends Controller {
         return $behaviors;
     }
 
-    public function actionJoin() {
+    /**
+     * @return array
+     * @throws ForbiddenOperationException
+     * @throws IllegalArgumentException
+     */
+    public function actionJoin(): array {
         Yii::$app->response->format = Response::FORMAT_JSON;
 
         $data = Yii::$app->request->post();
         $protocol = new ModernJoin($data['accessToken'] ?? '', $data['selectedProfile'] ?? '', $data['serverId'] ?? '');
         $joinForm = new JoinForm($protocol);
-        $joinForm->join();
+        $joinForm->join(); // will throw an exception in case of any error
 
         return ['id' => 'OK'];
     }
 
-    public function actionJoinLegacy() {
+    public function actionJoinLegacy(): string {
         Yii::$app->response->format = Response::FORMAT_RAW;
 
         $data = Yii::$app->request->get();
@@ -64,7 +71,12 @@ class SessionController extends Controller {
         return 'OK';
     }
 
-    public function actionHasJoined() {
+    /**
+     * @return array
+     * @throws ForbiddenOperationException
+     * @throws IllegalArgumentException
+     */
+    public function actionHasJoined(): array {
         Yii::$app->response->format = Response::FORMAT_JSON;
 
         $data = Yii::$app->request->get();
@@ -76,7 +88,7 @@ class SessionController extends Controller {
         return $textures->getMinecraftResponse();
     }
 
-    public function actionHasJoinedLegacy() {
+    public function actionHasJoinedLegacy(): string {
         Yii::$app->response->format = Response::FORMAT_RAW;
 
         $data = Yii::$app->request->get();
@@ -95,7 +107,14 @@ class SessionController extends Controller {
         return 'YES';
     }
 
-    public function actionProfile($uuid) {
+    /**
+     * @param string $uuid
+     *
+     * @return array
+     * @throws ForbiddenOperationException
+     * @throws IllegalArgumentException
+     */
+    public function actionProfile(string $uuid): array {
         try {
             $uuid = Uuid::fromString($uuid)->toString();
         } catch (\InvalidArgumentException $e) {
diff --git a/api/modules/session/models/HasJoinedForm.php b/api/modules/session/models/HasJoinedForm.php
index da5a2ee..d6a547b 100644
--- a/api/modules/session/models/HasJoinedForm.php
+++ b/api/modules/session/models/HasJoinedForm.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace api\modules\session\models;
 
 use api\modules\session\exceptions\ForbiddenOperationException;
@@ -6,19 +8,27 @@ use api\modules\session\exceptions\IllegalArgumentException;
 use api\modules\session\models\protocols\HasJoinedInterface;
 use api\modules\session\Module as Session;
 use common\models\Account;
+use Webmozart\Assert\Assert;
 use Yii;
-use yii\base\ErrorException;
 use yii\base\Model;
 
 class HasJoinedForm extends Model {
 
+    /**
+     * @var HasJoinedInterface
+     */
     private $protocol;
 
     public function __construct(HasJoinedInterface $protocol, array $config = []) {
-        $this->protocol = $protocol;
         parent::__construct($config);
+        $this->protocol = $protocol;
     }
 
+    /**
+     * @return Account
+     * @throws ForbiddenOperationException
+     * @throws IllegalArgumentException
+     */
     public function hasJoined(): Account {
         Yii::$app->statsd->inc('sessionserver.hasJoined.attempt');
         if (!$this->protocol->validate()) {
@@ -38,10 +48,9 @@ class HasJoinedForm extends Model {
         }
 
         $joinModel->delete();
+        /** @var Account $account */
         $account = $joinModel->getAccount();
-        if ($account === null) {
-            throw new ErrorException('Account must exists');
-        }
+        Assert::notNull($account);
 
         Session::info("User with username = '{$username}' successfully verified by server with server_id = '{$serverId}'.");
         Yii::$app->statsd->inc('sessionserver.hasJoined.success');
diff --git a/api/modules/session/models/JoinForm.php b/api/modules/session/models/JoinForm.php
index bc4e2ad..29764ca 100644
--- a/api/modules/session/models/JoinForm.php
+++ b/api/modules/session/models/JoinForm.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace api\modules\session\models;
 
 use api\modules\session\exceptions\ForbiddenOperationException;
@@ -11,8 +13,8 @@ use common\helpers\StringHelper;
 use common\models\Account;
 use common\models\MinecraftAccessKey;
 use Ramsey\Uuid\Uuid;
+use Webmozart\Assert\Assert;
 use Yii;
-use yii\base\ErrorException;
 use yii\base\Model;
 use yii\web\UnauthorizedHttpException;
 
@@ -35,15 +37,14 @@ class JoinForm extends Model {
     private $protocol;
 
     public function __construct(JoinInterface $protocol, array $config = []) {
+        parent::__construct($config);
         $this->protocol = $protocol;
         $this->accessToken = $protocol->getAccessToken();
         $this->selectedProfile = $protocol->getSelectedProfile();
         $this->serverId = $protocol->getServerId();
-
-        parent::__construct($config);
     }
 
-    public function rules() {
+    public function rules(): array {
         return [
             [['accessToken', 'serverId'], RequiredValidator::class],
             [['accessToken', 'selectedProfile'], 'validateUuid'],
@@ -51,7 +52,12 @@ class JoinForm extends Model {
         ];
     }
 
-    public function join() {
+    /**
+     * @return bool
+     * @throws IllegalArgumentException
+     * @throws ForbiddenOperationException
+     */
+    public function join(): bool {
         $serverId = $this->serverId;
         $accessToken = $this->accessToken;
         Session::info("User with access_token = '{$accessToken}' trying join to server with server_id = '{$serverId}'.");
@@ -62,9 +68,7 @@ class JoinForm extends Model {
 
         $account = $this->getAccount();
         $sessionModel = new SessionModel($account->username, $serverId);
-        if (!$sessionModel->save()) {
-            throw new ErrorException('Cannot save join session model');
-        }
+        Assert::true($sessionModel->save());
 
         Session::info("User with access_token = '{$accessToken}' and nickname = '{$account->username}' successfully joined to server_id = '{$serverId}'.");
         Yii::$app->statsd->inc('sessionserver.join.success');
@@ -72,7 +76,14 @@ class JoinForm extends Model {
         return true;
     }
 
-    public function validate($attributeNames = null, $clearErrors = true) {
+    /**
+     * @param string $attributeNames
+     * @param bool $clearErrors
+     *
+     * @return bool
+     * @throws IllegalArgumentException
+     */
+    public function validate($attributeNames = null, $clearErrors = true): bool {
         if (!$this->protocol->validate()) {
             throw new IllegalArgumentException();
         }
@@ -80,7 +91,12 @@ class JoinForm extends Model {
         return parent::validate($attributeNames, $clearErrors);
     }
 
-    public function validateUuid($attribute) {
+    /**
+     * @param string $attribute
+     *
+     * @throws IllegalArgumentException
+     */
+    public function validateUuid(string $attribute): void {
         if ($this->hasErrors($attribute)) {
             return;
         }
@@ -91,18 +107,19 @@ class JoinForm extends Model {
     }
 
     /**
-     * @throws \api\modules\session\exceptions\SessionServerException
+     * @throws \api\modules\session\exceptions\ForbiddenOperationException
      */
-    public function validateAccessToken() {
+    public function validateAccessToken(): void {
         $accessToken = $this->accessToken;
         /** @var MinecraftAccessKey|null $accessModel */
-        $accessModel = MinecraftAccessKey::findOne($accessToken);
+        $accessModel = MinecraftAccessKey::findOne(['access_token' => $accessToken]);
         if ($accessModel !== null) {
             Yii::$app->statsd->inc('sessionserver.authentication.legacy_minecraft_protocol');
             /** @var MinecraftAccessKey|\api\components\OAuth2\Entities\AccessTokenEntity $accessModel */
             if ($accessModel->isExpired()) {
                 Session::error("User with access_token = '{$accessToken}' failed join by expired access_token.");
                 Yii::$app->statsd->inc('sessionserver.authentication.legacy_minecraft_protocol_token_expired');
+
                 throw new ForbiddenOperationException('Expired access_token.');
             }
 
@@ -117,6 +134,7 @@ class JoinForm extends Model {
             if ($identity === null) {
                 Session::error("User with access_token = '{$accessToken}' failed join by wrong access_token.");
                 Yii::$app->statsd->inc('sessionserver.join.fail_wrong_token');
+
                 throw new ForbiddenOperationException('Invalid access_token.');
             }
 
@@ -124,6 +142,7 @@ class JoinForm extends Model {
             if (!Yii::$app->user->can(P::MINECRAFT_SERVER_SESSION)) {
                 Session::error("User with access_token = '{$accessToken}' doesn't have enough scopes to make join.");
                 Yii::$app->statsd->inc('sessionserver.authentication.oauth2_not_enough_scopes');
+
                 throw new ForbiddenOperationException('The token does not have required scope.');
             }
 
@@ -135,12 +154,14 @@ class JoinForm extends Model {
         if ($isUuid && $account->uuid !== $this->normalizeUUID($selectedProfile)) {
             Session::error("User with access_token = '{$accessToken}' trying to join with identity = '{$selectedProfile}', but access_token issued to account with id = '{$account->uuid}'.");
             Yii::$app->statsd->inc('sessionserver.join.fail_uuid_mismatch');
+
             throw new ForbiddenOperationException('Wrong selected_profile.');
         }
 
         if (!$isUuid && mb_strtolower($account->username) !== mb_strtolower($selectedProfile)) {
             Session::error("User with access_token = '{$accessToken}' trying to join with identity = '{$selectedProfile}', but access_token issued to account with username = '{$account->username}'.");
             Yii::$app->statsd->inc('sessionserver.join.fail_username_mismatch');
+
             throw new ForbiddenOperationException('Invalid credentials');
         }