A developer's atlas of distributed commit, isolation, and the choreography of state.
A transaction is the smallest indivisible motion of meaning across a system. We treat the verb commit with the gravity of a notary: every observed change must be undoable until the moment it isn't. Between BEGIN and COMMIT lies a small kingdom of provisional truth.
BEGIN;
UPDATE accounts SET balance = balance - 100 WHERE id = 'A';
UPDATE accounts SET balance = balance + 100 WHERE id = 'B';
COMMIT;Snapshot, repeatable read, serializable — each level is a treaty between throughput and truth. The discipline is to pick a level and write the system that earns it. We dwell on phantom reads, write skew, and the geometry of conflict graphs.
A consistency model is a contract written in the negative — what shall never appear. The work of transactology is to translate these refusals into checks, constraints, and proofs. From referential integrity to causal order, the rules accumulate like marginalia in a well-loved textbook.
Write-ahead logs, fsync barriers, replication quorums — the apparatus by which a fact survives the loss of its container. In this chapter we audit the path from RAM to platter, from log buffer to cold archive, treating each hop as a potential betrayal.
A network of transaction endpoints. Pulses travel along committed paths. Hover a node to read its ledger card.
A horizontal scrollable shelf. Each spine is a doorway into deeper material.