LibraryConsensus2001Design paperCorpus record
Paxos Made Simple
Paxos Made Simple. Leslie Lamport.
The same two-phase majority protocol, written as pseudocode: prepare, accept, and learn.
A reading of the public document. Not a copy of it, and not a claim about a later network that reused the name.
Use this, not a blog summary, when someone claims a log is Paxos. The safety rule is the promise, not the word consensus.
The five-minute read
The defect
The original parliament paper is hard to implement from. Engineers needed the algorithm without the metaphor.
The rule
The same two-phase majority protocol, written as pseudocode: prepare, accept, and learn.
How it is put together
One leader can run many instances, one per log slot. Acceptors are the memory. Learners are the readers. A value sticks once a majority has accepted it.
Where the claim stops
The note is not a failure detector.
One action, walked through
- The proposer picks a number higher than any it has used.
- Acceptors promise not to accept a lower number and report any accepted value.
- The proposer then asks them to accept a single safe value.
- Is each log slot its own decision?
The argument, unpacked
Why it is still on the desk
Use this, not a blog summary, when someone claims a log is Paxos. The safety rule is the promise, not the word consensus.
After the text
Production systems added leases, batching and reconfiguration. Those are extra. The ballot rule is the paper.
What has to be true
- The note is not a failure detector.
- It does not tell you how to choose the leader.
- It does not make a network synchronous.
What happened after the paper
Production systems added leases, batching and reconfiguration. Those are extra. The ballot rule is the paper.
What to check before you use the idea
- Is each log slot its own decision?
- What happens if two proposers use the same number?
- Do learners wait for a majority or for the leader?
Terms
- Acceptor
- A replica that stores promises and accepted values.
- Proposer
- A process that tries to get one value chosen.
The problem the paper names
The original parliament paper is hard to implement from. Engineers needed the algorithm without the metaphor.
What the design proposes
- One leader can run many instances, one per log slot.
- Acceptors are the memory. Learners are the readers.
- A value sticks once a majority has accepted it.
How the mechanism is specified
- The proposer picks a number higher than any it has used.
- Acceptors promise not to accept a lower number and report any accepted value.
- The proposer then asks them to accept a single safe value.
What this page does not treat as proven
- The note is not a failure detector.
- It does not tell you how to choose the leader.
- It does not make a network synchronous.
Why a venture studio still reads it
Use this, not a blog summary, when someone claims a log is Paxos. The safety rule is the promise, not the word consensus.
This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.
Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.