# Design exercise: Query Execution & Optimization

> Logical and physical plans, cardinality estimation, join ordering, indexes, vectorized execution, and spilling. Implement designOutline() returning non-empty values for: logicalPlan, costModel, physicalExecution. Each value must name a concrete mechanism or decision.

Canonical: https://learn.significanthobbies.com/curriculum/drills/practice-query-execution-optimization

Logical and physical plans, cardinality estimation, join ordering, indexes, vectorized execution, and spilling. Implement designOutline() returning non-empty values for: logicalPlan, costModel, physicalExecution. Each value must name a concrete mechanism or decision.

## The mechanism

A query optimizer searches physical plans using imperfect estimates. Execution quality depends on access paths, join order, memory budgets, and fallback under estimation error.

## Expected evidence

A design outline with logicalPlan, costModel, physicalExecution plus an explicit failure mode or trade-off.

## Hints

- Name the failure mode before selecting the mechanism.

## Sources and practice

- [Architecture of a Database System](https://dsf.berkeley.edu/papers/fntdb07-architecture.pdf)
- [Study Query Execution & Optimization](https://learn.significanthobbies.com/curriculum/concepts/query-execution-optimization)
- [Try the interactive drill](https://learn.significanthobbies.com/drills/practice-query-execution-optimization)
- [All practice briefs](https://learn.significanthobbies.com/curriculum/drills/)