Recap and Feedback
In this part, you studied three themes that matter strongly in real database-backed systems: correctness during multi-step work, schema quality, and performance. You learned why transactions matter, how concurrency can produce silent wrong results, why redundancy creates anomalies, how normalization repairs them, when denormalization is the right deliberate exception, what indexes do for performance, and how to verify with EXPLAIN ANALYZE that a change actually helped.
The part ended with two project checkpoints, each walking the toolkit through a different concrete feature. The first checkpoint built a card-at-a-time study mode and focused on transactional atomicity — making the rating-recording write either fully happen or fully not, even if anything fails partway through. The second checkpoint built a move-card-between-decks feature and focused on isolation under concurrent access — using SELECT ... FOR UPDATE to lock the target deck and source card so two simultaneous moves cannot corrupt each other. The two checkpoints exercised the same toolkit on visibly different features, but each one verified a different transaction concern in depth: atomicity in the first, concurrency-safe locking in the second. Together they cover the two genuinely distinct kinds of transactional correctness this part introduced.
The project has, with these checkpoints, gone from a tool that manages decks and cards to a working study tracker that the user can actually use to study, that handles concurrent operations safely, and that stays fast as the data grows. Each of the three themes — transactions, schema quality, performance — is visible in the project.
Along the way, this part also gave the discipline of verification one more application: after every change, check that the change does what it was meant to do. That habit — run EXPLAIN ANALYZE after adding an index, simulate a failure to confirm a transaction rolls back, hold a lock in psql to confirm a route blocks — ties everything in this part together.
Recap Quiz
The recap quiz below is a short sequence of questions drawn from the main ideas of this part. Complete it before the feedback form.
Feedback
Next, please take a moment to reflect on your work in this part and provide feedback. Your input helps us improve the course materials.