@danchia I went through code for memtable . Just have few doubts

1. is memtable lock free skiplist ?
2. does memtable only support insert operation ?

it is just a question ... for your opinion is there no way for merging LSM-tree with WAL considering they work appending ?

I can see Replicate vs Paxos or Raft in the roadmap, but I think it's overkill for replication as there seems to be an easier and faster way to accomplish that - see CURP (Consistent Unordered Replication Protocol).

What Paxos or Raft is good for is distributed transactions in a sharded environment (aka horizontal partitioning). In this case there is currently no known way how to do it more efficiently than using Paxos or Raft for updating a distributed ledger keeping the information about success or failure of such transaction (see FaunaDB as tested by Jepsen).

i d like understand better how work a mvcc, it is a important part in a db design. :)