WordPress Gutenberg Performance - Disable Block Editor Preload Paths

gutenberg-performance.php

<?php

namespace Gutenberg_Performance;

/**
 * Removes the Synced Patterns (reusable blocks) from the preload paths.
 * Performance improvement for sites with large number of these blocks.
 *
 * @param array $paths Paths.
 *
 * @return array
 */
function block_editor_rest_api_preload_paths( $paths ) {
	return array_values(
		array_filter(
			$paths,
			function ( $v ) {
				return ! is_string( $v ) || ! str_starts_with( $v, '/wp/v2/blocks?context=edit' );
			},
		)
	);
}
add_filter( 'block_editor_rest_api_preload_paths', __NAMESPACE__ . '\block_editor_rest_api_preload_paths', 999, 1 );

See Enhancing WordPress Stability: Addressing Gutenberg Block Editor Preloading Issues for further context.

This issue is being addressed in WordPress 6.7, see Gutenberg PR #58239, #64459