[free-ekanayaka]

Depends on how fast is your disk, what file system and kernel you use, and how low is your network latency. Difficult to predict. But it's basically as fast as it can get given 1) hardware constraints 2) raft consensus.

If you want light-speed insert/delete, you could probably don't use the disk at all: as long as a majority of your nodes don't die, you won't lose any data. You can also go somewhere in between and save to disk only at specific intervals.

[zellyn]

Do all nodes participate as full RAFT nodes? Or can you have read-only nodes?

[setr]

Aren't non-leader RAFT nodes already read-only?

[zellyn]

I guess I meant observer nodes, with read-only DB access.

[setr]

I just mean that RAFT nodes are already read-only for most of their lives — it’s not clear to me why you’d want nodes to be dedicated as read-only; it would only reduce consistency guarantees (and I believe you wouldn’t be avoiding the heartbeat and data consistency network chatter).. I think the leadership functionality comes cheap

[zellyn]

That makes sense. I need to read up on Raft again.

I know Zookeeper, for example, supports observer nodes: essentially a cheaper read-only cache. Chubby at Google had the same thing.