I tried but seems aws has closed the door. To connect ec2 to Lightsail via private IP I have to create a "ec2-classic VPC" in ec2. But aws has disabled "ec2-classic VPC" in all regions
This pricing only seems make sense when the two instances are belong to different owners that are billed $0.01/GB both. But still ridiculous: Data transfer in from internet is free, but from another zones/regions cost $0.01. Maybe they just want to make the pricing "look cheaper"?
Installed, and uninstalled when I found it automatically add it's icon to my dock. (It's the first mac software I ever installed that add it's icon to dock itself)
Off-topic question, what software your social site is based on? or developed by your own? I think a social site should allow members to post casual post to encourage interactions. Maybe you can try some more Facebook-style platforms like Jcow(https://www.jcow.net ) to rebuild your site.
For Compute Droplets there are "standard droplet" using shared cpu and "optimized droplet" can use 100% of a cpu. Then for the databases, can user use 100% cpu even for $15 plan?