[dtech]

How difficult it is to scale depends on your requirements, but if those aren't strict it's as easy as adjusting a parameter. In my experience it's not hard at all.

If you can live with not strictly ordered messages around scale time you just rescale. If you can live with some latency you stop producing, wait until lag is zero, scale, and then start producing again.

Plus if you pick a partition number with nice divisors like 6, 12, 20, 24, 40 or 60 you can have balanced consumption with different number of consumers.

[raducu]

I really like your number of partitions with nice divisors, I thought of it myself and enthusiastically raved about it to an architect (which I really respect for a lot of reasons) but he insisted on some formula about throughput and I dropped the idea. Truth be told, I work for a bank with fixed number of servers.