How to load multiple nodes in Drupal 8 and perform operations on field

You can use the following snippet to load multiple nodes without getting timeout or memory-related issues.

use Drupal\node\Entity\Node; 
$nids = \Drupal::entityQuery('node')->condition('type', 'YOUR_CONTENT_TYPE')->execute();
$nodes = Node::loadMultiple($nids);
foreach ($nodes as $node) {  
  // Perform field-related operations.
  $field_value = $node->field_machine_name->getValue()[0]
}