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Lesson plan 46: Spanner, CockroachDB, and FoundationDB
Compare Spanner, CockroachDB, and FoundationDB through distributed transaction responsibilities.
Placement: Part 8: Architectural case studies and synthesis.
Prerequisites: Lesson 45: Redis and memory-oriented designs, plus the earlier dependency chain.
Learning outcomes
- Compare Spanner, CockroachDB, and FoundationDB through distributed transaction responsibilities.
- Explain timestamp uncertainty, replicated ranges, and separated transaction/storage roles within their documented scope.
- Identify which locality and coordination costs remain after local execution improves.
- Separate a general mechanism, a documented implementation choice, and an illustrative numerical assumption.
Teaching sequence
- Establish the motivating situation: A globally correct transfer crosses regions while unrelated tenants can remain local.
- Introduce the vocabulary and the correctness obligation before an optimization. Define distributed transactions, timestamps, replication.
- Develop the mechanism: Contrast documented architectural mechanisms and historical scope without inventing a universal performance ranking.
- Follow the complete worked example: With a 70 ms remote quorum path, a 5 ms local execution improvement cannot remove that 70 ms path. Explain the assumptions, intermediate units, and limiting interpretation.
- Extend the scenario to changed load, skew, or failure, explaining placement, coordination, layering.
- Connect the mechanism to a documented implementation and an alternative with a different workload fit. Close by stating the remaining cost and the next lesson dependency.
Required chapter material
Use a complete execution trace or worked calculation, supported by an annotated static diagram or table. Include language-neutral pseudocode or labeled SQL when it clarifies the mechanism. State preconditions, ownership, visibility, and failure boundaries for algorithms. Describe operational costs as well as the normal path. All questions raised in the narrative must be resolved in the text.
Visual explanation
A comparison matrix maps transaction ordering, conflict handling, replication, placement, and application interface to each architecture without inventing a common benchmark. The accompanying prose explains the arrows, state changes, or table entries so the lesson remains understandable in a plain Markdown reader.
Editorial checks
Confirm that the numerical example agrees with its units and assumptions. Check that a faster path preserves the stated contract, or explicitly identify the changed guarantee. Keep hypothetical figures separate from product measurements. Explain both an appropriate use and a limitation of the case design. Check terminology against the glossary and links against the course index.