Day 6Level 1 — Core Mental Models
CAP and PACELC: The Theory You Actually Need
Learn: 45 minMap: 30 minDesign: 60 min
Core Concepts (5)
- 1.CAP: under partition, choose Consistency or Availability — not both
- 2.PACELC: even without partition, choose Latency or Consistency (ELC)
- 3.Most systems aren't in partition most of the time — PACELC matters more daily
- 4.CP systems: Spanner, etcd, ZooKeeper — latency varies under partition
- 5.AP systems: Dynamo, Cassandra, Riak — conflicts resolved on read
Map to Your Experience
For your system's data stores: which are CP, which are AP? What happens to latency and consistency during a network partition?
Design Brief: Data Store Consistency Classification
Requirements
- •Classify all data stores
- •Document consistency model per store
- •Describe partition behavior
- •Identify PACELC trade-off per store
Constraints
- •Use real system or realistic design
- •Reference actual technologies used
Must Cover
cp-ap-classificationconsistency-modelspartition-behaviorpacelc-tradeoff
Trade-off Axis
consistency guarantees vs latency/availability
Referenced Patterns
Competencies Advanced
data state → L2distribution communication → L2
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