Diego Ongaro's Raft paper[1]. Perhaps this only speaks to my experience as a student but having surveyed some of the other papers in the domain (paxos[2] in its many variants: generalized paxos[3], fpaxos[4], epaxos[5], qleases[6]), I'm glad the author expended the effort he did in making Raft as understandable (relatively) as it is.

[1]: https://raft.github.io/raft.pdf

[2]: https://www.microsoft.com/en-us/research/wp-content/uploads/...

[3]: https://www.microsoft.com/en-us/research/wp-content/uploads/...

[4]: https://www.microsoft.com/en-us/research/wp-content/uploads/...

[5]: https://www.cs.cmu.edu/~dga/papers/epaxos-sosp2013.pdf

[6]: https://www.cs.cmu.edu/~dga/papers/leases-socc2014.pdf