The API Gateway is a CPT initiative to create a rate-limited API proxy at api.wikimedia.org as part of the Platform Evolution program. The MVP scope includes the MediaWiki REST API (including page, media, history, and search endpoints) and the Feeds API, with the intention of adding APIs over time. As of July 24, 2020, the initiative is in the implementation phase. See the initiative page and Phabricator tag.
https://www.mediawiki.org/wiki/Core_Platform_Team/Initiatives/API_Gateway/Documentation_Plan
https://www.mediawiki.org/wiki/Core_Platform_Team/Initiatives/Developer_Portal#Initiative_Vision