Well, the only real pointer I had was the reference architecture I linked to.
A few other tips:
A few other tips:
If your Moodle site has a lot of files, then Catalyst's objectfs plugin, which lets most of the uploaded files be stored in S3, rather than EFS, will probably save you money. However, we setup our site without that first, and got everything working, and then added objectfs later.
With Aurora Redis, it turns out that the resoruce constraints are tricky and not clearnly documented. In particular, network traffic is quoted as a 'burst' bandwidth. What this means if that you can only just that much bandwith for a small amout of time. If you exceed that, you get throttled! SO, if with high traffic, your site works for about 20 minutes, then grinds to a halt, this might be the cause (and you need to bigger Redis instance).
Anyway, as you say, just separating the web server and the DB is a good first step in moving away from everything-on-one-server. And Aurora DB-as-a-service is probably a good way to go down that route.