- Materialize is not really focused on scaling because that is not really what it is for

Horizontal scalability is actually something that Materialize's underlying incremental computation engine (timely/differential dataflow) excels at. We're actively working to expose that tech in Materialize. (As in: many engineers, including me, are working on this full time; happy to answer questions!)

It is too bad that you got the wrong impression from that blog post! That blog post is about two years out of date. We're working on an updated roadmap blog post. The tl;dr is that we've since moved from step 3 on the roadmap ("Build a single-node database management system") to step 4 ("Build cloud-native elasticity and replication: Materialize Cloud").