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Leader-based Sequence Paxos

Lecture notes that develop a practical consensus algorithm for agreeing on a sequence of decisions despite failures.

Motivation and approach

Replicated services need to agree on an ordered log of decisions even when processes fail. Practical consensus algorithms can be difficult to understand, so these notes build up from basic Paxos through a sequence of transformations, covering recovery and changes in membership.

My contribution

I co-authored the notes with Seif Haridi and Paris Carbone and contributed substantially to the algorithm, particularly its leader election.

Outcome

The resulting lecture notes were published on arXiv in 2020. They present a complete algorithm for sequence consensus, together with the steps that explain how it is constructed.