Distributed Consistency & Shared State¶
Primes about keeping multiple copies or participants' views of shared state aligned: consensus protocols and their agreement/validity/termination guarantees, consistency models such as eventual consistency and denormalization, and failure modes like configuration drift, deadlock, and inconsistent shared models.
11 primes in this family — primes that sit near one another in abstraction space (k-means over structural-signature embeddings). Each is shown with its short description.
- Configuration Drift — The silent, monotonic divergence between a system's recorded intended state and its actual running state, driven by accumulated out-of-band changes that bypass the record until a forced reconciliation exposes the gap.
- Consensus — Producing a single shared decided state from many participants with disagreeing or adversarial views, under a fault model, satisfying agreement, validity, and termination together.
- Consensus Problem
- Consistency — A set of commitments cannot jointly derive a contradiction.
- Consistency Model — An explicit contract over which observations of shared state are legal when updates are concurrent.
- Credible Commitment — Deliberately constrain your own future choices so a promise or threat stays incentive-compatible at the moment of execution.
- Deadlock — Mutual blocking processes.
- Denormalization — Deliberately re-introduce controlled redundancy against a canonical form, trading a synchronization burden for access-side wins.
- Eventual Consistency — Distributed copies of shared state are allowed to diverge under local updates, with a deterministic merge guaranteeing they reconverge once updates stop.
- Inconsistent Shared Model — Subsystems hold mutually incompatible models of the same external state, undetected until a forcing event requires joint action.
- Object Permanence — A system maintains persistent internal state for entities it cannot currently observe, modeling them as continuing to exist and re-binding them on re-emergence.