15-minute session: read for 3 minutes, trace for 3, experiment for 7, and complete the check for 2. Spend longer whenever you need.
A lock protects an invariant only when every relevant access follows the same rule. Protect the whole read-modify-write operation, not just the final assignment. Define a consistent lock order when multiple locks are needed. A global lock may be correct but limit throughput; measure before splitting it.
Practice and evidence: Predict the example or draw its state transitions. Change one assumption, test the boundary, and record the actual result. Explain what this small model does not establish about a production system.
Keep three notes: your prediction, the actual result, and why they match or differ. The completion check grades understanding; the practice task builds skill.