diff --git a/Classes/Command/SequenceCommandController.php b/Classes/Command/SequenceCommandController.php
index 076cd53..d57b4fc 100644
--- a/Classes/Command/SequenceCommandController.php
+++ b/Classes/Command/SequenceCommandController.php
@@ -1,8 +1,12 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Command;
 
+use DigiComp\Sequence\Domain\Model\Insert;
 use DigiComp\Sequence\Service\SequenceGenerator;
+use Doctrine\ORM\EntityManagerInterface;
 use Neos\Flow\Annotations as Flow;
 use Neos\Flow\Cli\CommandController;
 
@@ -14,21 +18,50 @@ use Neos\Flow\Cli\CommandController;
 class SequenceCommandController extends CommandController
 {
     /**
-     * @var SequenceGenerator
      * @Flow\Inject
+     * @var SequenceGenerator
      */
     protected $sequenceGenerator;
 
+    /**
+     * @Flow\Inject
+     * @var EntityManagerInterface
+     */
+    protected $entityManager;
+
     /**
      * Sets minimum number for sequence generator
      *
      * @param int $to
      * @param string $type
      */
-    public function advanceCommand($to, $type)
+    public function advanceCommand(int $to, string $type): void
     {
         $this->sequenceGenerator->advanceTo($to, $type);
     }
 
-    // TODO: make clean up job to delete all but the biggest number to save resources
+    /**
+     * @param string[] $typesToClean
+     */
+    public function cleanSequenceInsertsCommand(array $typesToClean = [])
+    {
+        $cleanArray = [];
+        if (empty($typesToClean)) {
+            $results = $this->entityManager
+                ->createQuery('SELECT i.type, MAX(i.number) max_number FROM ' . Insert::class . ' i GROUP BY i.type')
+                ->getScalarResult();
+            foreach ($results as $result) {
+                $cleanArray[$result['type']] = (int) $result['max_number'];
+            }
+        } else {
+            foreach ($typesToClean as $typeToClean) {
+                $cleanArray[$typeToClean] = $this->sequenceGenerator->getLastNumberFor($typeToClean);
+            }
+        }
+        foreach ($cleanArray as $typeToClean => $number) {
+            $this->entityManager
+                ->createQuery('DELETE FROM ' . Insert::class . ' i WHERE i.type = ?0 AND i.number < ?1')
+                ->execute([$typeToClean, $number]);
+        }
+    }
 }
diff --git a/Classes/Domain/Model/Insert.php b/Classes/Domain/Model/Insert.php
index 6e95e41..97b0cb8 100644
--- a/Classes/Domain/Model/Insert.php
+++ b/Classes/Domain/Model/Insert.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Domain\Model;
 
 use Doctrine\ORM\Mapping as ORM;
@@ -16,24 +18,24 @@ use Neos\Flow\Annotations as Flow;
 class Insert
 {
     /**
-     * @var int
      * @Flow\Identity
      * @ORM\Id
+     * @var int
      */
-    protected $number;
+    protected int $number;
 
     /**
-     * @var string
      * @Flow\Identity
      * @ORM\Id
+     * @var string
      */
-    protected $type;
+    protected string $type;
 
     /**
      * @param int $number
      * @param string|object $type
      */
-    public function __construct($number, $type)
+    public function __construct(int $number, $type)
     {
         $this->setNumber($number);
         $this->setType($type);
@@ -42,7 +44,7 @@ class Insert
     /**
      * @return int
      */
-    public function getNumber()
+    public function getNumber(): int
     {
         return $this->number;
     }
@@ -50,7 +52,7 @@ class Insert
     /**
      * @param int $number
      */
-    public function setNumber($number)
+    public function setNumber(int $number): void
     {
         $this->number = $number;
     }
@@ -58,7 +60,7 @@ class Insert
     /**
      * @return string
      */
-    public function getType()
+    public function getType(): string
     {
         return $this->type;
     }
@@ -66,10 +68,10 @@ class Insert
     /**
      * @param string|object $type
      */
-    public function setType($type)
+    public function setType($type): void
     {
-        if (is_object($type)) {
-            $type = get_class($type);
+        if (\is_object($type)) {
+            $type = \get_class($type);
         }
         $this->type = $type;
     }
diff --git a/Classes/Service/Exception.php b/Classes/Service/Exception.php
index 37b66ed..96a3ad7 100644
--- a/Classes/Service/Exception.php
+++ b/Classes/Service/Exception.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Service;
 
 /**
diff --git a/Classes/Service/SequenceGenerator.php b/Classes/Service/SequenceGenerator.php
index ba8a0ea..715e6ab 100644
--- a/Classes/Service/SequenceGenerator.php
+++ b/Classes/Service/SequenceGenerator.php
@@ -1,15 +1,15 @@
 <?php
 
+declare(strict_types=1);
+
 namespace DigiComp\Sequence\Service;
 
 use DigiComp\Sequence\Domain\Model\Insert;
-use Doctrine\Common\Persistence\ObjectManager;
-use Doctrine\DBAL\DBALException;
-use Doctrine\ORM\EntityManager;
+use Doctrine\DBAL\Exception as DBALException;
+use Doctrine\ORM\EntityManagerInterface;
 use Neos\Flow\Annotations as Flow;
-use Neos\Flow\Log\SystemLoggerInterface;
-use Neos\Flow\Reflection\ReflectionService;
 use Neos\Utility\TypeHandling;
+use Psr\Log\LoggerInterface;
 
 /**
  * A SequenceNumber generator working for transactional databases
@@ -22,29 +22,25 @@ use Neos\Utility\TypeHandling;
 class SequenceGenerator
 {
     /**
-     * @var ObjectManager
      * @Flow\Inject
+     * @var EntityManagerInterface
      */
     protected $entityManager;
 
     /**
-     * @var ReflectionService
-     * @Flow\Inject
-     * @deprecated
-     */
-    protected $reflectionService;
-
-    /**
-     * @var SystemLoggerInterface
      * @Flow\Inject
+     * @var LoggerInterface
      */
     protected $systemLogger;
 
     /**
      * @param string|object $type
+     *
      * @return int
+     * @throws Exception
+     * @throws DBALException
      */
-    public function getNextNumberFor($type)
+    public function getNextNumberFor($type): int
     {
         $type = $this->inferTypeFromSource($type);
         $count = $this->getLastNumberFor($type);
@@ -60,12 +56,11 @@ class SequenceGenerator
 
     /**
      * @param int $count
-     * @param string|object $type
+     * @param string $type
      * @return bool
      */
-    protected function validateFreeNumber($count, $type)
+    protected function validateFreeNumber(int $count, string $type): bool
     {
-        /* @var EntityManager $em */
         $em = $this->entityManager;
         try {
             $em->getConnection()->insert(
@@ -77,10 +72,10 @@ class SequenceGenerator
             return false;
         } catch (DBALException $e) {
             if (! $e->getPrevious() instanceof \PDOException) {
-                $this->systemLogger->logException($e);
+                $this->systemLogger->critical('Exception occured: ' . $e->getMessage());
             }
         } catch (\Exception $e) {
-            $this->systemLogger->logException($e);
+            $this->systemLogger->critical('Exception occured: ' . $e->getMessage());
         }
 
         return false;
@@ -89,9 +84,11 @@ class SequenceGenerator
     /**
      * @param int $to
      * @param string|object $type
+     *
      * @return bool
+     * @throws Exception
      */
-    public function advanceTo($to, $type)
+    public function advanceTo(int $to, $type): bool
     {
         $type = $this->inferTypeFromSource($type);
 
@@ -100,15 +97,17 @@ class SequenceGenerator
 
     /**
      * @param string|object $type
+     *
      * @return int
+     * @throws Exception
+     * @throws DBALException
      */
-    public function getLastNumberFor($type)
+    public function getLastNumberFor($type): int
     {
-        /* @var EntityManager $em */
-        $em = $this->entityManager;
-
-        return $em->getConnection()->executeQuery(
-            'SELECT MAX(number) FROM ' . $em->getClassMetadata(Insert::class)->getTableName() . ' WHERE type = :type',
+        return (int) $this->entityManager->getConnection()->executeQuery(
+            'SELECT MAX(number) FROM '
+                . $this->entityManager->getClassMetadata(Insert::class)->getTableName()
+                . ' WHERE type = :type',
             ['type' => $this->inferTypeFromSource($type)]
         )->fetchAll(\PDO::FETCH_COLUMN)[0];
     }
@@ -118,9 +117,9 @@ class SequenceGenerator
      * @return string
      * @throws Exception
      */
-    protected function inferTypeFromSource($stringOrObject)
+    protected function inferTypeFromSource($stringOrObject): string
     {
-        if (is_object($stringOrObject)) {
+        if (\is_object($stringOrObject)) {
             $stringOrObject = TypeHandling::getTypeForValue($stringOrObject);
         }
         if (! $stringOrObject) {
diff --git a/composer.json b/composer.json
index 9500219..806f08f 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,8 @@
     "license": "MIT",
     "homepage": "https://github.com/digicomp/DigiComp.Sequence",
     "require": {
-        "neos/flow": "~4.1|~5.3"
+        "neos/flow": "~5.3 | ^6.3.5",
+        "php": "^7.4"
     },
     "require-dev": {
         "phpunit/phpunit": "3.7.*",
@@ -33,7 +34,8 @@
     "extra": {
         "branch-alias": {
             "dev-version/1.x-dev": "1.1.x-dev",
-            "dev-develop": "2.0.x-dev"
+            "dev-version/2.x-dev": "2.1.x-dev",
+            "dev-develop": "3.0.x-dev"
         },
         "applied-flow-migrations": [
             "Inwebs.Basket-201409170938",
@@ -70,4 +72,4 @@
             "Neos.Flow-20180415105700"
         ]
     }
-}
\ No newline at end of file
+}