# Summary
- [Introduction](./introduction.md)
- [Overall Architecture](./architecture.md)
- [Module Overview](./modules/overview.md)
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- [Contributor's Guide](./contributing.md)
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- [SQL Front-End](./modules/sql.md)
- [Catalog](./modules/catalog.md)
- [Expression System](./modules/expression.md)
- [Query Plan](./modules/plan.md)
- [The Lifecycle of a Query](./plan/lifecycle.md)
- [Query Optimizer](./modules/optimizer.md)
- [Rule-Based Optimization](./optimizer/rules.md)
- [Execution Engine](./modules/execution.md)
- [The Volcano Model](./execution/volcano.md)
- [Transaction Manager](./modules/transaction.md)
- [MVCC and 2PL](./transaction/mvcc_and_2pl.md)
- [Front-Ends (CLI / HTTP)](./modules/bin.md)
- [Testing & Documentation](./modules/tests.md)