In a follow up blog post https://blog.cloudflare.com/http-analytics-for-6m-requests-p... Cloudflare released the following image https://blog.cloudflare.com/content/images/2018/03/Old-syste... with 'single instance PostgreSQL database (a.k.a. RollupDB), accepted aggregates from Zoneagg consumers and wrote them into temporary tables per partition per minute' as the description for the single Postgres instance depicted. The aggregation system described in the Citus blog distributes the aggregation work over multiple Postgres instances.
