Eventual-consistency UX: free-recall review
Free-recall prompts across the eventual-UX unit. Answer each in your own words first, then reveal the model answer and compare.
Retrieval beats re-reading. For each prompt, say or write a full answer from memory before you open the model answer — the effort of recall is what makes the material stick.
Reconstruct the unit’s core ideas — the consistency window, optimistic UI’s three-part contract, when to show a pending state, idempotent retries, and deliberate conflict resolution — without looking back at the lesson.
- 01What is the consistency window, and why does an async backend make it the frontend's problem?
- 02State the three-part contract of optimistic UI, and which part juniors skip.
- 03When is optimistic UI the wrong tool, and what do you show instead?
- 04Why does every pending state need a timeout, and what are the two failure modes that lurk here?
- 05Explain the LWW vs merge vs CRDT tradeoff for reconciling two concurrent async writes, and the frontend's job in each case.
- 06Why does 'POST then immediately refetch' break read-your-own-writes, and how do you keep the eventual refresh without the violation?
If you could reconstruct each answer from memory, you hold the unit’s spine: an async write moves the consistency window onto the frontend; optimistic UI’s apply-send-reconcile contract buys ~0ms perceived latency but is a lie without the rollback step; when the server owns the outcome you show an honest pending state guarded by a timeout; double-submits are made safe with an idempotency key; concurrent writes are reconciled deliberately (LWW for simple fields, CRDTs for shared text); and read-your-own-writes survives by echoing locally instead of trusting a racing refetch. Now when you design the next feature over an async backend, you can name the consistency window, pick the right contract for each action, and explain why to anyone who thinks a 202 means done.
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