If you’re doing a serious data load, I’d give it 32GB.
No. A single predicate is kept within one shard. See section 2.3 in Dgraph Whitepapers: In-Depth Insights and Analysis .
A single Alpha node can handle a lot. Behind it is Badger, which is being used to server TBs of data.
If ingestion speed is important, I’d suggest looking into ludicrous mode. I can’t find documentation on our docs yet, but you can see it as a flag on both Alpha and Zero in the latest release.