diff --git a/lib/private/DB/QueryBuilder/ExtendedQueryBuilder.php b/lib/private/DB/QueryBuilder/ExtendedQueryBuilder.php
index c40cadfbdb5f6..f928132a123a8 100644
--- a/lib/private/DB/QueryBuilder/ExtendedQueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/ExtendedQueryBuilder.php
@@ -289,12 +289,12 @@ public function executeStatement(?IDBConnection $connection = null): int {
 		return $this->builder->executeStatement($connection);
 	}
 
-	public function hintShardKey(string $column, mixed $value, bool $overwrite = false) {
+	public function hintShardKey(string $column, mixed $value, bool $overwrite = false): self {
 		$this->builder->hintShardKey($column, $value, $overwrite);
 		return $this;
 	}
 
-	public function runAcrossAllShards() {
+	public function runAcrossAllShards(): self {
 		$this->builder->runAcrossAllShards();
 		return $this;
 	}
diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index 6cdf97b01e9fc..3ee417733301e 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -560,7 +560,7 @@ public function addSelect(...$selects) {
 		return $this;
 	}
 
-	private function addOutputColumns(array $columns) {
+	private function addOutputColumns(array $columns): void {
 		foreach ($columns as $column) {
 			if (is_array($column)) {
 				$this->addOutputColumns($column);
@@ -1370,11 +1370,11 @@ public function escapeLikeParameter(string $parameter): string {
 		return $this->connection->escapeLikeParameter($parameter);
 	}
 
-	public function hintShardKey(string $column, mixed $value, bool $overwrite = false) {
+	public function hintShardKey(string $column, mixed $value, bool $overwrite = false): self {
 		return $this;
 	}
 
-	public function runAcrossAllShards() {
+	public function runAcrossAllShards(): self {
 		// noop
 		return $this;
 	}
diff --git a/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php b/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
index e7bc70ce440c3..e5b66470de08a 100644
--- a/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
@@ -296,7 +296,7 @@ private function registerOrder(string $column, string $order): void {
 		];
 	}
 
-	public function hintShardKey(string $column, mixed $value, bool $overwrite = false) {
+	public function hintShardKey(string $column, mixed $value, bool $overwrite = false): self {
 		if ($overwrite) {
 			$this->primaryKeys = [];
 			$this->shardKeys = [];
@@ -310,7 +310,7 @@ public function hintShardKey(string $column, mixed $value, bool $overwrite = fal
 		return $this;
 	}
 
-	public function runAcrossAllShards() {
+	public function runAcrossAllShards(): self {
 		$this->allShards = true;
 		return $this;
 	}
diff --git a/lib/private/Files/Cache/Cache.php b/lib/private/Files/Cache/Cache.php
index 0b0ff8ee4faa4..e1547fefe1cc5 100644
--- a/lib/private/Files/Cache/Cache.php
+++ b/lib/private/Files/Cache/Cache.php
@@ -1207,7 +1207,7 @@ public function getCacheEntryFromSearchResult(ICacheEntry $rawEntry): ?ICacheEnt
 		}
 	}
 
-	private function moveFromStorageSharded(ShardDefinition $shardDefinition, ICache $sourceCache, ICacheEntry $sourceEntry, $targetPath) {
+	private function moveFromStorageSharded(ShardDefinition $shardDefinition, ICache $sourceCache, ICacheEntry $sourceEntry, $targetPath): void {
 		if ($sourceEntry->getMimeType() === ICacheEntry::DIRECTORY_MIMETYPE) {
 			$fileIds = $this->getChildIds($sourceCache->getNumericStorageId(), $sourceEntry->getPath());
 		} else {
diff --git a/lib/private/Memcache/Factory.php b/lib/private/Memcache/Factory.php
index 931c871d0f140..370130912d676 100644
--- a/lib/private/Memcache/Factory.php
+++ b/lib/private/Memcache/Factory.php
@@ -6,6 +6,7 @@
  */
 namespace OC\Memcache;
 
+use Closure;
 use OCP\Cache\CappedMemoryCache;
 use OCP\ICache;
 use OCP\ICacheFactory;
@@ -40,7 +41,7 @@ class Factory implements ICacheFactory {
 	private IProfiler $profiler;
 
 	/**
-	 * @param callable $globalPrefixClosure
+	 * @param Closure $globalPrefixClosure
 	 * @param LoggerInterface $logger
 	 * @param ?class-string<ICache> $localCacheClass
 	 * @param ?class-string<ICache> $distributedCacheClass
@@ -48,7 +49,7 @@ class Factory implements ICacheFactory {
 	 * @param string $logFile
 	 */
 	public function __construct(
-		private $globalPrefixClosure,
+		private Closure $globalPrefixClosure,
 		LoggerInterface $logger,
 		IProfiler $profiler,
 		?string $localCacheClass = null,
diff --git a/lib/private/Preview/BackgroundCleanupJob.php b/lib/private/Preview/BackgroundCleanupJob.php
index acf7bf22f5259..44832a78eb91f 100644
--- a/lib/private/Preview/BackgroundCleanupJob.php
+++ b/lib/private/Preview/BackgroundCleanupJob.php
@@ -16,7 +16,6 @@
 use OCP\Files\NotFoundException;
 use OCP\Files\NotPermittedException;
 use OCP\IDBConnection;
-use function Symfony\Component\Translation\t;
 
 class BackgroundCleanupJob extends TimedJob {
 	/** @var IDBConnection */
diff --git a/lib/public/DB/QueryBuilder/IQueryBuilder.php b/lib/public/DB/QueryBuilder/IQueryBuilder.php
index 22724c0c8005e..a965e0b5390ec 100644
--- a/lib/public/DB/QueryBuilder/IQueryBuilder.php
+++ b/lib/public/DB/QueryBuilder/IQueryBuilder.php
@@ -1040,7 +1040,7 @@ public function getColumnName($column, $tableAlias = '');
 	 * @return $this
 	 * @since 30.0.0
 	 */
-	public function hintShardKey(string $column, mixed $value, bool $overwrite = false);
+	public function hintShardKey(string $column, mixed $value, bool $overwrite = false): self;
 
 	/**
 	 * Set the query to run across all shards if sharding is enabled.
@@ -1048,7 +1048,7 @@ public function hintShardKey(string $column, mixed $value, bool $overwrite = fal
 	 * @return $this
 	 * @since 30.0.0
 	 */
-	public function runAcrossAllShards();
+	public function runAcrossAllShards(): self;
 
 	/**
 	 * Get a list of column names that are expected in the query output
diff --git a/tests/lib/DB/QueryBuilder/Partitioned/PartitionedQueryBuilderTest.php b/tests/lib/DB/QueryBuilder/Partitioned/PartitionedQueryBuilderTest.php
index 88a3c1250449f..697b3ab92c980 100644
--- a/tests/lib/DB/QueryBuilder/Partitioned/PartitionedQueryBuilderTest.php
+++ b/tests/lib/DB/QueryBuilder/Partitioned/PartitionedQueryBuilderTest.php
@@ -51,7 +51,7 @@ private function getQueryBuilder(): PartitionedQueryBuilder {
 		}
 	}
 
-	private function setupFileCache() {
+	private function setupFileCache(): void {
 		$this->cleanupDb();
 		$query = $this->getQueryBuilder();
 		$query->insert('storages')
@@ -92,7 +92,7 @@ private function setupFileCache() {
 		$query->executeStatement();
 	}
 
-	private function cleanupDb() {
+	private function cleanupDb(): void {
 		$query = $this->getQueryBuilder();
 		$query->delete('storages')
 			->where($query->expr()->gt('numeric_id', $query->createNamedParameter(1000000, IQueryBuilder::PARAM_INT)));