magento 2 update index after adding product in code code example

Example 1: run partial indexing from command line magento 2

bin/magento cronmanager:runjob indexer_update_all_views

Example 2: reindex after post api magento 2

$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
    $indexerCollectionFactory = $objectManager->get("\Magento\Indexer\Model\Indexer\CollectionFactory");
    $indexerFactory = $objectManager->get("\Magento\Indexer\Model\IndexerFactory");

    $indexerCollection = $indexerCollectionFactory->create();
    $allIds = $indexerCollection->getAllIds();
    foreach ($allIds as $id) {
        $indexer = $indexerFactory->create()->load($id);
        $indexer->reindexAll();
    }