Hello!
I'd like to move my gaming community from PHPBB to NodeBB. I'm somewhat disappointed about the improvements of PHPBB the last few years, and would like to simplify a lot of things for the people that register to the forums.
To give an idea of the magnitude of my community forum, I've included the PHPBB forum stats. (Please do not hurt me for not updating my PHPBB forum :()
In our PHPBB forum the shoutbox is relatively active (I guess about 2 messages per hour on average, with peaks of 20 per hour)
I'm planning to deploy the NodeBB website to a VPS with 1GB of RAM and 1 vCore. Also, the hard drive is not an SSD. Currently the virtualization is OpenVZ, but I'm planning to move to a new KVM VPS soon (with SSD). I want to host the database (redis/mongo) and the website on the same VPS. Do you think the server will be sufficiently performant on this hosting plan? Or do I risk getting a lot of 503 error messages when it's in use?
Also: What database should I choose? Redis is certainly more performant, but I'm afraid that it gets out of memory very soon. What database size can I expect? Will MongoDB be a safer choice?
Can someone advise me about these problems? I can solve other problems (migrating, configuring etc.) for myself 
Additionally: I found that by default polling is preferred over websockets. Is it bad to prefer websockets over polling?
Moving your site to NodeBB shouldn't be a problem at all. What is more important is the server stack & the amount of connections you have.
Best would be to get a VPS at OVH for example. Their plans are cheap and work quite well (at least I use them for all my projects).
Additionally I would suggest you to check my "High performance stack" tutorial in the Tutorial section. It features a full description to configure a highly efficient server stack.
About Redis:
I have around 9k members and 42k posts.
My Redis instace is using 700MB RAM, which is just fine for the size of my machine.
Thank you both for your responses 
Does the redis database size scale linearly with the amount of users and posts, or are there other aspects that may increase the database size?
@AOKP I do agree on it that OVH certainly provides high-quality servers for their price with little downtime. Yet I've had lots of issues with their network (random package loss) and CPU (/proc/loadavg had very often 3.66/4 while I did nothing) when I had a VPS on their system (~ a year ago). I suspect that they oversell their VPS nodes with a factor of around 1.5, which fears me.
That's why I prefer a little more expensive host (with less RAM, eventually) 
(
@leaseweb)
@JasperNL Interesting, I actually had the same issues with OVH when I used them, which is why I don't usually recommend them. I guess mileage varies though, a lot of people love them.
@yariplus @JasperNL, alternatively you can use Kimsufi, which belongs to OVH to 100%. The only difference is that the systems there are dedicated ones and not virtual machines. I also use one of these for my download server, which works quite alright.
About Redis:
The database size itself will increase the same way as others. More data = bigger database. For more infos check this out:
