Highload Blocks (`highloadblock`)

Highload blocks (HL) are ORM-backed flat tables whose columns are user fields (UF_*). No sections/tree, no iblock SEO model. The name does not guarantee performance — it depends on fields, indexes, filters and volume.

\Bitrix\Main\Loader::includeModule('highloadblock'); // always before API use

When HL vs Iblock vs Custom Tablet

Need	Prefer
Flat dictionary / reference list, admin-editable UF structure, iblock "directory" source	Highload block
Sections, SEO, properties, public content UX	Iblock (`bitrix-iblocks`)
Schema fully owned by code, migrations, typed checks	Custom ORM tablet (`bitrix-orm`)