Most Citus workloads were 10s of TB with largest at around a few PB or so. Heap was a couple PB, back then, if I remember correctly. It is a brilliant piece of technology that supported mission critical workloads across mid/late stage startups to huge enterprises. The planner/executor are very advanced supporting a multitude of features and decade of intricate effort.

The biggest problem of Citus was migration effort, transition from single node to multi-node was not trivial. Here I’m not talking about single table use-cases, more classic relational, multi-tenant apps with 100s to 1000s of tables. This is partly expected with most sharding technologies, though.

Sharing some insights based on my multiple years of experience working with Citus!

Here are few customer use-cases I could found:

https://docs.citusdata.com/en/v10.0/get_started/what_is_citu...

https://info.citusdata.com/rs/235-CNE-301/images/Citus_Data_...?

https://www.youtube.com/watch?v=F6df3HV6kP0