Does Neon scale writes indefinetely?

Is Neon able to scale write operations indefinitely just like reads? That’s not yet clear to us.
If not, what write performance may we expect (IOPS/s)?

The short answer is no. You can have many read-only nodes, and you can have any writable branches, but only one Postgres node can be writing at a time on a particular branch. That said, with a large instance, you can do a lot of writes with a single Postgres node. Especially if you direct the reads to othet nodes.

We make no guarantees on write throughput, but our goal is that the storage system can absorb the writes at the speed that Postgres can generate the WAL. In other words, write performance should be the same as on a standalone Postgres installation on similar hardware.