Just wanted to call out and thank the badger authors for a great key value store! :)
I'm using badger at work (for an event aggregation system), and I've been able to get a throughput of 200k writes per second without any tuning on a single machine (4 SSD's on raid 0).
We're also planning on using it for OctoSQL[1] and are basing all our exactly-once streaming efforts on Badger transactions. (we'll see how that pans out in the future!).