It doesn’t look like a mistake if the title and post both say 1 million users. Anyway, you should change the topic title from “1M user at the same time” to “1K user at the same time” so you might attract someone with a similar load who could tell you what they are actually using. By the way, what is a “RAW server” - did you mean “RAM”?
Your assumption of a blog should be ignored because the forum should make higher demands on the server. But you still have to consider what users are actually doing:
anonymous vs logged-in
read vs post
There are a lot of useful topics about capacity and scaling in the hosting category. Here’s two guess-timates that may be in the same ball park:
But above those levels, there is this site that was running on 8 CPUs and 16GB RAM:
What service level(s) are you aiming at? This post/topic is my favorite because it compares Discourse with traditional (i.e. LAMP-based) forums:
Don’t forget that if you are cloud hosting then the size of the database becomes more relevant because you might have to spend more money to expand limited storage.
FYI, here’s some further info which might be relevant to your decision-making options:
You can simulate capacity on a Discourse site and see what happens:
Based on Google Analytics real time report I can serve around 450+ concurrent sessions using our UpCloud.com 6-core / 16GB RAM VPS. They have one of the fastest servers around. But this is obviously a guesstimate, as GAnalytics is not the most accurate way to measure this, and the number of user activity (participating / logged in / guest) varies case by case.
We have this busy day only once a year and always the hickups have started to occur somewhere around the 450 sessions marker on GAnalytics. If the site starts to choke the number of sessions naturally drops rapidly.
I have multiple forums running on the same server with around 40K signed up users on these forums.
Daily user access averages around a 1.5k to 2.5k users
Daily views averages around 20k to 26k views
Daily user to user replies averages around 3k to 5k
I am expecting this traffic to go much higher in future.
I have DB and Redis running on a separate servers
All servers have 4GB of RAM assigned to them.
Could someone give me a rough estimate of what kind of resources will be adequate this kind of traffic ?