6 methods override QueueWorkerInterface::processItem() in Drupal 8

AggregatorRefresh::processItem in core/modules/aggregator/src/Plugin/QueueWorker/AggregatorRefresh.php

Works on a single queue item.

CronQueueTestBrokenQueue::processItem in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestBrokenQueue.php

Works on a single queue item.

CronQueueTestException::processItem in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestException.php

Works on a single queue item.

CronQueueTestRequeueException::processItem in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestRequeueException.php

Works on a single queue item.

LocaleTranslation::processItem in core/modules/locale/src/Plugin/QueueWorker/LocaleTranslation.php

The translation update functions executed here are batch operations which are also used in translation update batches. The batch functions may need to be executed multiple times to complete their task, typically this is the translation import…

ThumbnailDownloader::processItem in core/modules/media/src/Plugin/QueueWorker/ThumbnailDownloader.php

Works on a single queue item.